Benzindene

Article abstract of DOI:10.1021/jo00288a041

A convenient route to benzindene (1) has been developed in which 2-methylnaphthalene is brominated sequentially in the α-position and the methyl group followed by application of a standard malonic ester route to propionic acid 10.Cyclization of 10 via the acid chloride gave 11 (76percent).Simultaneous reduction of the carbonyl group and hydrogenolysis of the aryl bromide linkage of 11 gave secondary alcohol 12 in 55.4percent yield.Sulfuric acid dehydration of 12 gave 1 (85percent).Less successful routes to 1 involved dithionite reduction of unsaturated sulfones 6.Dihydro derivative 7 could be synthesized in 72percent yield by magnesium/methanol reduction of 5b.