NUCLEAR ISOPRENYLATION OF POLYHYDROXYACETHOPHENONES ACID CATALYSED CONDENSATION WITH ISOPRENE

Article abstract of DOI:10.1016/S0040-4020(01)92463-9

A novel method of nuclear isoprenylation leading to the exclusive formation of 2,2-dimethylchromans has been achieved by the direct condensation of polyhydroxyacetophenones with isoprene in presence of phosphoric acid.Acetylchromans, thus obtained, are dehydrogenated with DDQ to given corresponding 2,2-dimethylchromenes.Using this method, synthesis of number of naturally occuring chromenes, viz. ripariochromene A (6), eupatoriochromene (10), encecalin (11), isoevodionol (16), evodionol (17) and methylevodionol (18) has been affected.