Musigmann, Klaus; Mayr, Herbert; Meijere, Armin de
Regio- and stereoselective ring-opening reactions of cyclopropenones. α-methylene-γ-butyrolactones via additions of trichlorocyclopropenylium ions to alkenes.
In: Tetrahedron Letters, Vol. 31, Nr. 9: S. 1261-1264
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.