Radical-mediated 5-exo-trig cyclizations of 3-silylhepta-1,6-dienes |
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Authors: | James Philippe Schenk Kurt Landais Yannick |
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Institution: | Laboratoire de Chimie Organique et Organométallique, Université Bordeaux-I, 351 Cours de la Libération, 33405 Talence Cedex, France. |
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Abstract: | 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 thiabicyclo3.3.0] skeleton in one step with excellent stereocontrol. |
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