Consecutive-6-endo trigonal cyclisations from polyene acyl radical intermediates leading to decalone and perhydrophenanthrone ring constructions

A range of substituted Se-phenyl 5,9-dieneselenoates, viz. 15a, 25, 26, 27, 42 and 52, have been synthesised and their reactions with Bu(3)SnH-AIBN investigated. The diene esters 15a, 42 and 52 are shown to lead to decalone and to perhydrophenanthrone derivatives, viz. 19, 43 and 53, respectively, via consecutive 6-endo trig modes of cyclisations starting from the corresponding 5,9-diene acyl radical intermediates. By contrast, the 5,9-dienoates 25 and 27 lacking alkyl substitution at C-9 instead underwent cyclisation to the indanones 36 and 37, respectively, and the 6-methyl substituted analogue 26 produced only the cyclopentanone 38 on treatment with Bu(3)SnH-AIBN.