Synthesis and mechanistic study of fused 2-pyrrolines via thermolysis of 6-substituted-3,5-hexadienyl azidoformates.
Thermolysis of 3,5-hexadienyl azidoformates at 300 degrees C, 0.05 Torr, led to a fused 2-pyrroline regiospecifically, regardless of the configuration E or Z between the C-3 and C-4 double bond. Thermolysis of 6-substituted-3,5(E)-hexadienyl azidoformates yielded a kinetically controlled 2-pyrroline with cis configuration between H-1 and H-8a whereas 6-substituted-3,5(Z)-hexadienyl azidoformates produced a cis and trans mixture. The mechanism was proposed as the loss of nitrogen to form an acyl nitrene, then addition to a double bond to produce an aziridine. Finally the cleavage of the C-C bond generated a vinylazomethine ylide followed by recyclization to a fused 2-pyrroline.
Wu
P L
PL
Department of Chemistry, National Cheng Kung University, Tainan, Taiwan 701, Republic of China. wupl@mail.ncku.edu.tw
Chung
T H
TH
Chou
Y
Y