Nitrene. Part XIII. Novel conversion of 2-nitrophenyl substituted butyrolactones into indoles with triethyl phosphite

Abstract

Reductive cyclization of α-(2-hydroxyethyl)-β-methoxy-o-nitrocinnamic acid γ-lactone (4) with triethyl phosphite produced 3,4-dihydro-5-methoxy[1,3]oxazino[3,4-a]indol-1-one (6), a new heterocyclic ring system. Reduction of 2-o-nitrobenzoyl-γ-butyrolactone (3) yielded 4,5-dihydro-1′H-spiro[furan-3,2′-indole]-2,3′-dione (8) as the major product, in addition to a trace amount of the 5-ethoxy-analogue of (6). Lactone (8) was hydrolysed and decarboxylated to give 1,2-dihydro-2-(2-hydroxyethyl)indol-3-one (9). These results provide a route to novel reactive heterocyclic lactones.