Reactions of α-alkyl- or α-halogeno-alkoxycarbonylmethylene(triphenyl)phosphoranes with phenanthrene-9, 10-quinone. Synthesis of phenanthro[9, 10-b]furan derivatives

Abstract

Reactions of the α-methyl substituted title ylides 2a, 2b with quinone 1 give the unexpected spiro-diastereoisomers 7 and 8 and the acrylates 9. Reactions of the α-ethyl and α-benzyl substituted ylides 2c and 2d with 1 afford compounds 4, 11 and 13, 14 respectively. Reaction between 1 and the α-halogeno substituted ylides 2e, 2f leads to formation of the diesters 16a and 16b respectively. All the fused furan derivatives obtained are formed via an initial Wittig monoolefination of 1 with the glide used.