Control of regioselectivity in nitrile oxide cycloadditions to cinnamic acid derivatives

Article abstract of DOI:10.1016/S0040-4039(00)78249-9

Tertiary cinnamides undergo cycloaddition with benzonitrile oxides producing the 5-phenyl and 4-phenyl regioisomers 2b and 3b in a 25-30:75-70 ratio. This result is opposite to that obtained utilizing methyl cinnamate 1a as the dipolarophile. A synthetically useful method for the preparation of the acid 3c, derived from what is usually the minor regioisomer, has been developed by taking advantage of this reversal of regiochemistry.