Danheiser Annulation
Encyclopedia
The Danheiser annulation or Danheiser TMS-cyclopentene annulation is an organic reaction
of an α,β-unsaturated ketone
and a trialkylsilylallene
(e.g., trimethylsilyl
- or triisopropylsilyl-) in the presence of a Lewis Acid
to give a trialkylsilylcyclopentene
in a regiocontrolled annulation
.
Organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...
of an α,β-unsaturated 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...
and a trialkylsilylallene
Allene
An allene is a compound in which one carbon atom has double bonds with each of its two adjacent carbon centres. Allenes are classified as polyenes with cumulated dienes. The parent compound of allene is propadiene. Compounds with an allene-type structure but with more than three carbon atoms are...
(e.g., trimethylsilyl
Trimethylsilyl
A trimethylsilyl group is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom [−Si3], which is in turn bonded to the rest of a molecule...
- or triisopropylsilyl-) in the presence of a Lewis Acid
Lewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
to give a trialkylsilylcyclopentene
Cyclopentene
Cyclopentene is a chemical compound with the formula 58. It is a colorless liquid with a petrol-like odor. It is one of the cycloalkenes.Cyclopentene is produced industrially in large amounts...
in a regiocontrolled annulation
Annulation
Annulation in organic chemistry is a chemical reaction in which a new ring is constructed on another molecule ....
.