One-pot synthesis of 1-aryl-3-methyl-1,3-dienes using methallyl(trimethyl)silane and aldehydes and their low temperature (Z)→(E) isomerization induced by sulfur dioxide |
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Authors: | Srinivas Reddy Dubbaka |
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Affiliation: | Laboratoire de glycochimie et de synthèse asymétrique, Ecole polytechnique Fédérale de Lausanne (EPFL), BCH CH-1015 Lausanne, Switzerland |
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Abstract: | 2-Methylprop-2-ene-1-sulfonyl fluorides can be easily prepared via the ene reaction of methallylsilanes and SO2. In the presence of a base, aldehydes and 2-methylprop-2-ene-1-sulfonyl fluorides give 1,3-(E) and (Z)-dienes. Their (Z)→(E) isomerization by classical means fails or leads to their polymerization. It is shown that SO2 can isomerize 1-aryl-3-methyl-1,3-dienes at low temperature, without formation of sulfolenes (cheletropic addition/elimination). Preliminary mechanistic studies suggest that SO2 adds to 1,3-dienes forming 1,4-diradical intermediates that are responsible for the (Z)→(E) isomerizations. |
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Keywords: | Aldehydes Diradical intermediates Ene reaction Methallylsilane (Z)&rarr (E)-Isomerization Sulfonyl fluoride Sulfur dioxide |
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