Cyclopropanation of N-Substituted 2-Oxochromene-3-carboxamides and 3-Oxobenzo[f]chromene-2-carboxamides with Bromine-containing Zinc Enolate Prepared from α,α -Dibromopinacolin and Zinc

Abstract

Zinc enolate obtained from 1,1-dibromo-3,3-dimethylbutan-2-one reacted with N-substituted 2-oxochromene-3-carboxamides and 3-oxobenzo[f]chromene-2-carboxamides affording 1-(2,2-dimethyl-propanoyl)-2-oxo-1a, 7b-dihydrocyclopropa[c]chromene-1a-carboxamides and 1-(2,2-dimethylpropanoyl)-2-oxo-1a, 9C-dihydrobenzo[f]cyclopropa[c]chromene-1a-carboxamide as single isomers.