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Musigmann, Klaus; Mayr, Herbert and Meijere, Armin de (1990): Regio- and stereoselective ring-opening reactions of cyclopropenones. α-methylene-γ-butyrolactones via additions of trichlorocyclopropenylium ions to alkenes. In: Tetrahedron Letters, Vol. 31, No. 9: pp. 1261-1264 [PDF, 231kB]


The 2-chloro-3-(2′-chloroalkyl)cyclopropenones 4, readily obtained by hydrolysis of the adducts of the trichlorocyclopropenylium ion onto alkenes, thermally rearrange to propiolic acid chlorides 6. Treatment of 4 with TosOH·H2O in CH2Cl2 yields the (E)-3-chloro-2-(2′-chloroalkyl)acrylic acids 9, which have been converted in two simple steps to -methylene-γ-butyrolactones 11 with good overall yields.

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