Bromination of 9-dimedonyltetrahydroxanthenone as a route to a new type of substituted hydrochromeno[2,3,4-kl]xanthenones

Abstract

Bromination of 9 dimedonyl 3,3 dimethyl 2,3,4,9 tetrahydro 1H xanthen 1 one was car ried out to provide a route to a new series of substituted hydrochromeno[2,3,4 kl]xanthenones, which may find application for the synthesis of poorly accessible compounds including the heteroanalogs. A dependence of transformations of dimedonyltetrahydroxanthenone on the nature of the solvent was elucidated: bromination at the α methylene groups of the dimedonyl substituent is accompanied by heterocyclization involving 1 and 5 oxo groups. Quantum chemical HF/6 311(d,p) ab initio calculations for the proposed mechanism of hemiacetalization and halogenation were carried out.