Indenone synthesis. Improved synthetic protocol and effect of substitution on the intramolecular Friedel–Crafts acylation

Abstract

An improved protocol for the construction of substituted indenones is presented. Also the effect of substitution on the intramolecular Friedel–Crafts acylation was noted. Specifically, if there is no substitution at the 2-position of the indenone poor yields of cyclized material were obtained, if at all, while the substitution of a methyl or ethyl group greatly improved the yield of cyclized material. Placement of a large group (e.g., benzyl) resulted in a diminuation of the improved yield. The new synthetic procedure could, in principle, allow for the construction of 2,3-disubstituted indenones. One example of this reaction mode was presented.