Oppenauer oxidation
Encyclopedia
Oppenauer oxidation, named after Rupert Viktor Oppenauer, is a gentle method for selectively oxidizing secondary alcohol
s to ketone
s.
The reaction is the opposite of Meerwein-Ponndorf-Verley reduction
. The alcohol is oxidized with aluminium isopropoxide
in excess acetone
. This shifts the equilibrium
toward the product side.
The oxidation is highly selective for secondary alcohols and does not oxidize other sensitive functional groups such as amine
s and sulfide
s. Though primary alcohol
s can be oxidized under Oppenauer conditions, primary alcohol
s are seldom oxidized by this method due to the competing aldol condensation
of aldehyde
products. The Oppenauer oxidation is still used for the oxidation of acid labile substrates. The method has been largely displaced by oxidation methods based on chromate
s (e.g. PCC
) or dimethyl sulfoxide
(e.g. Swern oxidation
) or Dess-Martin oxidation due to its use of relatively mild and non-toxic reagents (e.g. the reaction is run in acetone/benzene mixtures). The Oppenanuer oxidation is commonly used in various industrial processes such as the synthesis of steroid
s, hormone
s, alkaloid
s, terpene
s, etc.
In the first step of the mechanism
, the alcohol
(1) coordinates to the aluminum to form a complex (3), which then, in the second step, gets deprotonated by an alkoxide
ion (4) to generate an alkoxide
intermediate
(5). In the third step, both the oxidant acetone
(7) and the substrate
alcohol
are bound to the aluminum. The acetone
is coordinated to the aluminum which activates it for the hydride
transfer from the alkoxide
. The aluminium-catalyzed hydride
shift from the α-carbon of the alcohol
to the carbonyl
carbon
of acetone
proceeds over a six-membered transition state
(8). The desired ketone
(9) is formed after the hydride
transfer.
/benzene
mixtures. Another advantage of the Oppenauer oxidation which makes it unique to other oxidation methods such as Pyridinium chlorochromate
(PCC) and Dess-Martin periodinane
is that secondary alcohols are oxidized much faster than primary alcohols, thus chemoselectivity
can be achieved. Furthermore, there is no over oxidation of aldehyde
s to carboxylic acid
s as opposed to another oxidation methods such the Jones oxidation
.
s are oxidized to Δ 4,6-3-ketosteroids with benzoquinone as the hydrogen
acceptor. This reaction is useful in that it affords a one-step preparation of Δ 4,6-3-ketosteroids.
for the aluminum alkoxide
. The Woodward modification of the Oppenauer oxidation is used when certain alcohol
groups do not become oxidized under the standard Oppenauer reaction conditions. For example, Wooward used potassium tert-butoxide
and benzophenone
for the oxidation of quinine
to quininone, as the traditional aluminum catalytic system failed to oxidize quinine
due to the complex formed by coordination of the Lewis-basic nitrogen
to the aluminum centre.
catalysts have been also reported. For example, a highly active aluminum catalyst was reported by Maruoka and co-workers which was utilized in the oxidation of carveol
to carvone
(a member of a family of chemicals called terpenoid
s) in excellent yield (94%).
In another modification the catalyst is trimethylaluminium
and the aldehyde
2-nitrobenzaldehyde
is used as the oxidant, for example, in the oxidation of isoborneol to camphor
.
s in the pharmaceutical industry such as morphine
and codeine
. For instance, codeinone
is prepared by the Oppenauer oxidation codeine
.
The Oppenauer oxidation is also used to synthesize hormones. Progesterone
is prepared by the Oppenauer oxidation of pregnenolone
.
A slight variation of the Oppenauer oxidation is also used to synthesize steroid
derivatives. For example, an efficient catalytic version of the Oppenauer oxidation which employs a ruthenium
catalyst has been developed for the oxidation of 5-unsaturated 3â-hydroxy steroid
s to the corresponding 4-en-3-one derivative.
The Oppenauer oxidation is also used in the synthesis
of lactones from 1,4 and 1,5 diol
s.
of the Oppenauer oxidation is the base
catalyzed aldol condensation
of aldehyde
products, which have α-hydrogen
s to form either ß-hydroxy aldehyde
s or α, ß-unsaturated aldehyde
s.
Another side reaction
is the Tischenko reaction of aldehyde
products with no α-hydrogen
, but this can be prevented by use of anhydrous
solvents. Another general side reaction is the migration of the double bond during the oxidation of allylic alcohol substrates.
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s to ketone
Ketone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
s.
The reaction is the opposite of Meerwein-Ponndorf-Verley reduction
Meerwein-Ponndorf-Verley reduction
The Meerwein-Ponndorf-Verley Reduction in organic chemistry is the reduction of ketones and aldehydes to their corresponding alcohols utilizing aluminumalkoxide catalysis in the presence of a sacrificial alcohol...
. The alcohol is oxidized with aluminium isopropoxide
Aluminium isopropoxide
Aluminium isopropoxide is the chemical compound usually described with the formula Al3, where i-Pr is the isopropyl group . This colourless solid is a useful reagent in organic synthesis...
in excess acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
. This shifts the equilibrium
Chemical equilibrium
In a chemical reaction, chemical equilibrium is the state in which the concentrations of the reactants and products have not yet changed with time. It occurs only in reversible reactions, and not in irreversible reactions. Usually, this state results when the forward reaction proceeds at the same...
toward the product side.
The oxidation is highly selective for secondary alcohols and does not oxidize other sensitive functional groups such as amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
s and sulfide
Sulfide
A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...
s. Though primary alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s can be oxidized under Oppenauer conditions, primary alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s are seldom oxidized by this method due to the competing aldol condensation
Aldol condensation
An aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a dehydration to give a conjugated enone....
of aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
products. The Oppenauer oxidation is still used for the oxidation of acid labile substrates. The method has been largely displaced by oxidation methods based on chromate
Chromate
Chromate salts contain the chromate anion, CrO42−. Dichromate salts contain the dichromate anion, Cr2O72−. They are oxyanions of chromium in the oxidation state +6. They are moderately strong oxidizing agents.- Chemical properties :...
s (e.g. PCC
Pyridinium chlorochromate
Pyridinium chlorochromate is a reddish orange solid reagent used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones. Pyridinium chlorochromate, or PCC, will not fully oxidize a primary alcohol to the carboxylic acid as does the Jones reagent. A disadvantage to using PCC is...
) or dimethyl sulfoxide
Dimethyl sulfoxide
Dimethyl sulfoxide is an organosulfur compound with the formula 2SO. This colorless liquid is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water...
(e.g. Swern oxidation
Swern oxidation
The Swern oxidation, named after Daniel Swern, is a chemical reaction whereby a primary or secondary alcohol is oxidized to an aldehyde or ketone using oxalyl chloride, dimethyl sulfoxide and an organic base, such as triethylamine...
) or Dess-Martin oxidation due to its use of relatively mild and non-toxic reagents (e.g. the reaction is run in acetone/benzene mixtures). The Oppenanuer oxidation is commonly used in various industrial processes such as the synthesis of steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
s, hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s, alkaloid
Alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
s, terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
s, etc.
Mechanism
In the first step of the mechanism
Mechanism
Mechanism may refer to:*Mechanism , rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission*Mechanism , explaining how a feature is created...
, the alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
(1) coordinates to the aluminum to form a complex (3), which then, in the second step, gets deprotonated by an alkoxide
Alkoxide
An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They can be written as RO−, where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands...
ion (4) to generate an alkoxide
Alkoxide
An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They can be written as RO−, where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands...
intermediate
Intermediate
Intermediate means "occurring between two extremes, or in the middle of a range". It comes from the Latin word 'intermedia' which literally means 'among the middle' and may refer to:...
(5). In the third step, both the oxidant acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
(7) and the substrate
Substrate (chemistry)
In chemistry, a substrate is the chemical species being observed, which reacts with a reagent. This term is highly context-dependent. In particular, in biochemistry, an enzyme substrate is the material upon which an enzyme acts....
alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
are bound to the aluminum. The acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
is coordinated to the aluminum which activates it for the hydride
Hydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
transfer from the alkoxide
Alkoxide
An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They can be written as RO−, where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands...
. The aluminium-catalyzed hydride
Hydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
shift from the α-carbon of the alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
to the carbonyl
Carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups....
carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
of acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
proceeds over a six-membered transition state
Transition state
The transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest energy along this reaction coordinate. At this point, assuming a perfectly irreversible reaction, colliding reactant molecules will always...
(8). The desired ketone
Ketone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
(9) is formed after the hydride
Hydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
transfer.
Advantages of Use
An advantage of the Oppenauer oxidation is its use of relatively inexpensive and non-toxic reagents. Reaction conditions are mild and gentle since the substrates are generally heated in acetoneAcetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
/benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
mixtures. Another advantage of the Oppenauer oxidation which makes it unique to other oxidation methods such as Pyridinium chlorochromate
Pyridinium chlorochromate
Pyridinium chlorochromate is a reddish orange solid reagent used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones. Pyridinium chlorochromate, or PCC, will not fully oxidize a primary alcohol to the carboxylic acid as does the Jones reagent. A disadvantage to using PCC is...
(PCC) and Dess-Martin periodinane
Dess-Martin periodinane
Dess–Martin periodinane is a chemical reagent used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones. This periodinane has several advantages over chromium- and DMSO-based oxidants that include milder conditions , shorter reaction times, higher yields, simplified workups,...
is that secondary alcohols are oxidized much faster than primary alcohols, thus chemoselectivity
Chemoselectivity
Chemical reactions are defined usually in small contexts , such generalizations are a matter of utility. The preferential outcome of one instance of a generalized reaction over a set of other plausible reactions, is defined as chemoselectivity...
can be achieved. Furthermore, there is no over oxidation of aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s to carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
s as opposed to another oxidation methods such the Jones oxidation
Jones oxidation
The Jones oxidation, is an organic reaction for the oxidation of primary and secondary alcohols to carboxylic acids and ketones, respectively. It is named after its discoverer, Sir Ewart Jones....
.
Wettstein-Oppenauer Reaction
In the Wettstein-Oppenauer reaction, discovered by Wettstein in 1945, Δ 5-3b-hydroxy steroidSteroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
s are oxidized to Δ 4,6-3-ketosteroids with benzoquinone as the hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
acceptor. This reaction is useful in that it affords a one-step preparation of Δ 4,6-3-ketosteroids.
Woodward Modification
In the Woodward modification, Woodward substituted potassium tert-butoxidePotassium tert-butoxide
Potassium tert-butoxide is the chemical compound with the formula 3COK. This colourless solid is a strong base useful in organic synthesis. It exists as a tetrameric cubane-like cluster...
for the aluminum alkoxide
Alkoxide
An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They can be written as RO−, where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands...
. The Woodward modification of the Oppenauer oxidation is used when certain alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
groups do not become oxidized under the standard Oppenauer reaction conditions. For example, Wooward used potassium tert-butoxide
Potassium tert-butoxide
Potassium tert-butoxide is the chemical compound with the formula 3COK. This colourless solid is a strong base useful in organic synthesis. It exists as a tetrameric cubane-like cluster...
and benzophenone
Benzophenone
Benzophenone is the organic compound with the formula 2CO, generally abbreviated Ph2CO. Benzophenone is a widely used building block in organic chemistry, being the parent diarylketone.-Uses:...
for the oxidation of quinine
Quinine
Quinine is a natural white crystalline alkaloid having antipyretic , antimalarial, analgesic , anti-inflammatory properties and a bitter taste. It is a stereoisomer of quinidine which, unlike quinine, is an anti-arrhythmic...
to quininone, as the traditional aluminum catalytic system failed to oxidize quinine
Quinine
Quinine is a natural white crystalline alkaloid having antipyretic , antimalarial, analgesic , anti-inflammatory properties and a bitter taste. It is a stereoisomer of quinidine which, unlike quinine, is an anti-arrhythmic...
due to the complex formed by coordination of the Lewis-basic nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
to the aluminum centre.
Other Modifications
Several modified aluminum alkoxideAlkoxide
An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They can be written as RO−, where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands...
catalysts have been also reported. For example, a highly active aluminum catalyst was reported by Maruoka and co-workers which was utilized in the oxidation of carveol
Carveol
Carveol is a natural unsaturated, monocyclic monoterpenoid alcohol that is a constituent of spearmint essential oil in the form of cis--carveol. It is a colorless fluid soluble in water and oils, but insoluble in water and has an odor and flavor that resemble those of spearmint and caraway...
to carvone
Carvone
Carvone is a member of a family of chemicals called terpenoids. Carvone is found naturally in many essential oils, but is most abundant in the oils from seeds of caraway and dill.-Stereoisomerism and odor:...
(a member of a family of chemicals called terpenoid
Terpenoid
The terpenoids , sometimes called isoprenoids, are a large and diverse class of naturally occurring organic chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways. Most are multicyclic structures that differ from one another not only in...
s) in excellent yield (94%).
In another modification the catalyst is trimethylaluminium
Trimethylaluminium
Trimethylaluminium is the chemical compound with the formula Al26, abbreviated as Al2Me6, 2 or the abbreviation TMA. This pyrophoric, colorless liquid is an industrially important organoaluminium compound...
and the aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
2-nitrobenzaldehyde
2-Nitrobenzaldehyde
2-Nitrobenzaldehyde is an organic aromatic compound containing a nitro group ortho to formyl. 2-Nitrobenzaldehyde once was produced as an intermediate in the synthesis of the popular dye Indigo.-Synthesis:...
is used as the oxidant, for example, in the oxidation of isoborneol to camphor
Camphor
Camphor is a waxy, white or transparent solid with a strong, aromatic odor. It is a terpenoid with the chemical formula C10H16O. It is found in wood of the camphor laurel , a large evergreen tree found in Asia and also of Dryobalanops aromatica, a giant of the Bornean forests...
.
Synthetic Applications
The Oppenauer oxidation is used to prepare analgesicAnalgesic
An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....
s in the pharmaceutical industry such as morphine
Morphine
Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...
and codeine
Codeine
Codeine or 3-methylmorphine is an opiate used for its analgesic, antitussive, and antidiarrheal properties...
. For instance, codeinone
Codeinone
Codeinone is 1/3 as active as codeine as an analgesic but it is an important intermediate in the production of hydrocodone, a painkiller about 3/4 the potency of morphine.-Chemical structure:...
is prepared by the Oppenauer oxidation codeine
Codeine
Codeine or 3-methylmorphine is an opiate used for its analgesic, antitussive, and antidiarrheal properties...
.
The Oppenauer oxidation is also used to synthesize hormones. Progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
is prepared by the Oppenauer oxidation of pregnenolone
Pregnenolone
Pregnenolone is a steroid hormone involved in the steroidogenesis of progesterone, mineralocorticoids, glucocorticoids, androgens, and estrogens. As such it is a prohormone. Pregnenolone sulfate is a GABAA antagonist and increases neurogenesis in the hippocampus.-Chemistry:Like other steroids,...
.
A slight variation of the Oppenauer oxidation is also used to synthesize steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
derivatives. For example, an efficient catalytic version of the Oppenauer oxidation which employs a ruthenium
Ruthenium
Ruthenium is a chemical element with symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most chemicals. The Russian scientist Karl Ernst Claus discovered the element...
catalyst has been developed for the oxidation of 5-unsaturated 3â-hydroxy steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
s to the corresponding 4-en-3-one derivative.
The Oppenauer oxidation is also used in the synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
of lactones from 1,4 and 1,5 diol
Diol
A diol or glycol is a chemical compound containing two hydroxyl groups A geminal diol has two hydroxyl groups bonded to the same atom...
s.
Side Reactions
A common side reactionReaction
Reaction may refer to:Response to another event*Adverse drug reaction*Chemical reaction*Emotional reaction*Light reaction*Nuclear reaction*TNA Reaction, a documentary show of TNA behind scenes.*Reaction , as defined by Newton's third law...
of the Oppenauer oxidation is the base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
catalyzed aldol condensation
Aldol condensation
An aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a dehydration to give a conjugated enone....
of aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
products, which have α-hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
s to form either ß-hydroxy aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s or α, ß-unsaturated aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s.
Another side reaction
Reaction
Reaction may refer to:Response to another event*Adverse drug reaction*Chemical reaction*Emotional reaction*Light reaction*Nuclear reaction*TNA Reaction, a documentary show of TNA behind scenes.*Reaction , as defined by Newton's third law...
is the Tischenko reaction of aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
products with no α-hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
, but this can be prevented by use of anhydrous
Anhydrous
As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...
solvents. Another general side reaction is the migration of the double bond during the oxidation of allylic alcohol substrates.
See also
- Meerwein-Ponndorf-Verley reductionMeerwein-Ponndorf-Verley reductionThe Meerwein-Ponndorf-Verley Reduction in organic chemistry is the reduction of ketones and aldehydes to their corresponding alcohols utilizing aluminumalkoxide catalysis in the presence of a sacrificial alcohol...
- Dess-Martin oxidation
- PCCPyridinium chlorochromatePyridinium chlorochromate is a reddish orange solid reagent used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones. Pyridinium chlorochromate, or PCC, will not fully oxidize a primary alcohol to the carboxylic acid as does the Jones reagent. A disadvantage to using PCC is...
- Jones oxidationJones oxidationThe Jones oxidation, is an organic reaction for the oxidation of primary and secondary alcohols to carboxylic acids and ketones, respectively. It is named after its discoverer, Sir Ewart Jones....
- Aldol condensationAldol condensationAn aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a dehydration to give a conjugated enone....