Radical-mediated 5-exo-trig cyclizations of 3-silylhepta-1,6-dienes.
Regioselectivity of the sulfonyl radical mediated 5-exo-trig cyclization of 3-silylheptadienyl systems 3a-d has been studied. At low temperature, the reaction of the sulfonyl radical occurs regioselectively at the allylsilane terminus, while a reversal of regioselectivity is observed at 80 degrees C. This general trend has been rationalized on the basis of polar effects and radical stabilization. Thiyl-mediated radical cyclization of dienes 3a, 3c-d, 7 with subsequent sulfur atom transfer was also studied, providing thiabicyclo[3.3.0] skeleton in one step with excellent stereocontrol.
James
Philippe
P
Laboratoire de Chimie Organique et Organométallique, Université Bordeaux-I, 351 Cours de la Libération, 33405 Talence Cedex, France.
Schenk
Kurt
K
Landais
Yannick
Y