DeMayo Reaction | Oranic Name Reaction

Theory and Destination :

DeMayo reaction is a photo chemical reaction in which the enol of a 1,3-di-ketone reacts with an

alkene (or another species with a C=C bond) and the resulting cyclobutane ring undergoes a retro-

aldol reaction to yield a 1,5-di ketone.

General Reaction :

Mechanism :

A visible light mediated DeMayo reaction between 1,3-di ketones and styrenes following a [2+2] 

cycloaddition pathway via a photosensitization mechanism gives access to 1,5-di ketones. The 

reaction has been applied to substituted styrenes and aryl- and alkyl-substituted ketones.

The net effect is to add the two carbon atoms in the C=C double bond between the two carbonyl

groups of the diketone. It is thus useful in syntheses both as a relatively selective way to join two

parts of a molecule and as a way to apply the more developed chemistry of 1,3-diketone synthesis to

1,5-diketones. The first part is a [2+2] cycloaddition. The ensuing retro-aldol cleavage is favored by

the relative instability of the cyclobutane ring.

Example and Applications :

1.An application to the total synthesis of ingenol, where the fused 7-7-5 ring system was constructed

by the cycloaddition-fragmentation sequence[1].

2.

1.Hoffmann, N. Chem. Rev. 2008, 108, 1052. DOI: 10.1021/cr0680336