SYNTHESIS OF 2,2-DIMETHYL 2H-PYRANO-FLAVONOL AND PYRANOCHROMONE DERIVATIVES

Diaroyl methane derivatives (1a-c) on performic acid oxidation in chlo roform yielded the corresponding 3,4 dihydro-2-2-dimethyl-2H pyranofla vonols (2a-c). 7-Hydroxy-2-methyl chromone (3) on prenylation with 3-m ethyl-2-buten-1-ol in the presence of boron trifluoride etherate yield ed a mixture of two compounds 7-hydroxy-6-C-prenyl-2-methyl chromone ( 4) and 6,7 dihydro-4H-2,8,8-trimethyl pyrano (3,2-g) chrom-4-one (5). The compound (4 and 5) on cycle dehydrogenation with DDQ afforded the corresponding dehydro product, 2,8,8-trimethyl pyrano (3,2-g) chrom-4- one (6).