Reactions of enynes with three or two ester groups (1-4) in the presence of halogen-ligand Lewisacids gave cyclized products with halide incorporation (5-8) with high generality. The cyclization process was also analyzed in a theoretical study. Facile isomerization and dehydrohalogenation of five-membered products 5 and 8 by Al(2)O(3) or Et(3)N were also observed; this process introduces conjugated
A novel cycloisomerization reaction of enynes 4 in the
presence of ZnBr2 and THF (1 eq.) in
CH2Cl2 at −40 °C gave
exo-methylenic 1,3-dienes 5 in moderate to good yield.