Hemiaminal
Encyclopedia
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
or type of chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
that has a hydroxyl group and an 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 Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group.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,...
attached to the same 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...
atom: -C(OH)(NR2)-. R can be 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...
or an alkyl group. Hemiaminals are intermediates in imine
Imine
An imine is a functional group or chemical compound containing a carbon–nitrogen double bond, with the nitrogen attached to a hydrogen atom or an organic group. If this group is not a hydrogen atom, then the compound is known as a Schiff base...
formation from an 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 Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group.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,...
and a 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....
by alkylimino-de-oxo-bisubstitution
Alkylimino-de-oxo-bisubstitution
Alkylimino-de-oxo-bisubstitution in organic chemistry is the organic reaction of carbonyl compounds with amines to imines . The reaction name is based on the IUPAC Nomenclature for Transformations...
.
An example is of an hemiaminal is that obtained from reaction of secondary amine carbazole
Carbazole
Carbazole is an aromatic heterocyclic organic compound. It has a tricyclic structure, consisting of two six-membered benzene ring fused on either side of a five-membered nitrogen-containing ring...
and formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
Reaction rate
The reaction rate or speed of reaction for a reactant or product in a particular reaction is intuitively defined as how fast or slow a reaction takes place...
comparable to a intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
reaction and also due to restricted access of external base (another amine) to the same cavity which would favor elimination
Elimination reaction
An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism...
of water to the imine.
Hemiaminal formation is a key step in an asymmetric total synthesis
Total synthesis
In organic chemistry, a total synthesis is, in principle, the complete chemical synthesis of complex organic molecules from simpler pieces, usually without the aid of biological processes. In practice, these simpler pieces are commercially available in bulk and semi-bulk quantities, and are often...
of saxitoxin
Saxitoxin
Saxitoxin is a neurotoxin naturally produced by certain species of marine dinoflagellates and cyanobacteria Saxitoxin (STX) is a neurotoxin naturally produced by certain species of marine dinoflagellates (Alexandrium sp., Gymnodinium sp., Pyrodinium sp.) and cyanobacteria Saxitoxin (STX) is a...
:
In this reaction step the alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
group is first oxidized to an intermediate acyloin
Acyloin
Acyloins are a class of organic compounds in organic chemistry sharing a common functional group consisting of a hydroxyl group placed on the α-position of a carbonyl group.- Nomenclature :Common types of ketols include:...
by action of osmium(III) chloride, oxone (sacrificial catalyst) and sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
(base).