N. F. Abdul-Malik, S. Awad, A. B. Sakla
Sep 19, 1979
Citations
0
Influential Citations
4
Citations
Journal
Helvetica Chimica Acta
Abstract
Reactions of acids with vinylidenexanthenes (or thioxanthenes) 1 and 9-methoxy-9-vinylxanthenes (or thioxanthenes) 8 give xanthene- (or thioxanthene-) 9-spiro-1′-indenes 7. With bromine or sulfuryl chloride they give the corresponding 2′-halogenoxanthene- (or thioxanthene-)9-spiro-1′-indenes 5. Formation of such derivatives depends on preferential attack of the reagents on allenes 1 to give initially xanthylium (or thioxanthylium) ions 3 which cyclize. One π bond of the allenes 1 can be selectively reduced in acid media. Chemical and spectral evidence for these routes are presented.