The intramolecular reaction between a diazoalkane group and an ester group: the first example

Abstract

Methyl cis-β-(3-diazo-1,2,2-trimethylcyclopentyl)acrylate (2) decomposed in alcoholic solvents to give an insertion product, methyl 4,7,7-trimethylbicyclo[2.2.1]hept-2-ene-1-carboxylate (6), in addition to the solvolysis products arising from protonation of the diazoalkane and described in the preceding paper. This is the first example of a reaction between a diazoalkane group and an ester group, and is similar to the well-known reaction of diazomethane with ketones. A study of the effect of solvent on the reaction led to an isolated yield of 89% of the bicyclic product. The less acidic the alcohol solvent, the slower the reaction and the more bicyclic product there is. In polar aprotic solvents such as acetonitrile the azine corresponding to the diazoalkane (2) is the major product.