Woodward cis-hydroxylation
Encyclopedia
The Woodward cis-hydroxylation is the chemical reaction
of alkene
s with iodine
and silver acetate
in wet acetic acid
to form cis-diols. The reaction is named after its discoverer, Robert Burns Woodward
.
This reaction has found application in steroid
synthesis
.
by acetic acid (or silver acetate) to give the first intermediate, the iodo-acetate (4). Through anchimeric assistance, the iodine is displaced via another SN2 reaction to give an oxonium ion
(5), which is subsequently hydrolyzed to the give the mono-ester (6).
The mono-ester can be hydrolyzed using potassium hydroxide
to form the corresponding diol
.
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
of alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s with iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
and silver acetate
Silver acetate
Silver acetate is a photosensitive, white crystalline substance commonly used as a pesticide. It also produces a repulsive taste when combined with cigarette smoke, so it is used in chewing gum and lozenges to aid the cessation of smoking.-Isolation:Silver acetate, the silver salt form of acetic...
in wet acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
to form cis-diols. The reaction is named after its discoverer, Robert Burns Woodward
Robert Burns Woodward
Robert Burns Woodward was an American organic chemist, considered by many to be the preeminent organic chemist of the twentieth century...
.
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...
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...
.
Reaction mechanism
The reaction of the iodine with the alkene is catalyzed by the silver acetate, thus forming an iodinium ion (3). The iodinium ion is opened via SN2 reactionSN2 reaction
The SN2 reaction is a type of nucleophilic substitution, where a lone pair from a nucleophile attacks an electron deficient electrophilic center and bonds to it, expelling another group called a leaving group. Thus the incoming group replaces the leaving group in one step...
by acetic acid (or silver acetate) to give the first intermediate, the iodo-acetate (4). Through anchimeric assistance, the iodine is displaced via another SN2 reaction to give an oxonium ion
Oxonium ion
The oxonium ion in chemistry is any oxygen cation with three bonds. The simplest oxonium ion is the hydronium ion H3O+. Another oxonium ion frequently encountered in organic chemistry is obtained by protonation or alkylation of a carbonyl group e.g...
(5), which is subsequently hydrolyzed to the give the mono-ester (6).
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
to form the corresponding 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...
.