Sequential addition reaction of lithium acetylides and Grignard reagents to thioiminium salts from thiolactams leading to 2,2-disubstituted cyclic amines

Abstract

Abstract The reaction of thioiminium salts derived from γ- and δ-thiolactams with lithium acetylides and Grignard reagents proceeded sequentially to give 2,2-disubstituted pyrrolidines and piperidines in moderate to high yields. In the initial step of the reaction, 2-(methylthio)pyrrolidines and -piperidines may be formed. The use of lithium (trimethylsilyl)acetylide gave the products most effectively. Aryl-, alkyl-, and allylmagnesium halides were used as Grignard reagents. Silylcarbocyclization of N -allyl 2-ethynyl cyclic amines with HSiMe 2 Ph in the presence of a catalytic amount of Rh 4 (CO) 12 was carried out to give trisubstituted hexahydro-1 H -pyrrolizines and octahydroindolizines.