Cyclization of dialkylpropyn‐1‐yl(allyl)(3‐isopropenylpropyn‐2‐yl)ammonium bromides and water‐base cleavage of 2,2‐dialkyl‐5‐methyl‐2,6,7,7 a ‐tetrahydro‐1 h ‐isoindolium and 2,2‐dialkyl‐5‐methylisoindolinium bromides

Dialkylpropyn‐1‐yl(or allyl)(3‐isopropenylpropyn‐2‐yl)ammonium bromides under base‐catalyzed condition instantly undergo intramolecular cyclization. The cyclization of dialkylpropyn‐1‐yl(3‐isopropenylpropyn‐2‐yl)ammonium bromides leads to the formation of 2,2‐dialkyl‐5‐methylisoindolinium salts. In case of allyl analogs, instead of the expected 2,2‐dialkyl‐6‐methyl‐3 a ,4‐dihydroisoindolinium salts their isomeric forms ‐ 2,2‐dialkyl‐5‐methyl‐2,6,7,7 a ‐tetrahydro‐1 H ‐isoindolium bromides are obtained. In alkaline medium they are transform into the dihydroisoindolinium salts, the cleavage of which in two directions ‐ 1,2 and 1,6 leads to the mixture of isomeric dialkyl‐1,4‐dimethyl‐ and 2,4‐dimethylbenzyl‐amines. Study of the behavior of 2,2‐dialkyl‐5‐methylisoindolinium salts under conditions of water‐base cleavage showed, that only spiro[5‐methylisoindolyn]morpholinium bromide undergoes 1,2‐elimination, forming 5‐methylisoindoline 2‐vinyl ethyl ester.