Hetero-Diels-Alder reactions of new sulfonylsulfines generated from α-substituted methylsulfones
نویسندگان
چکیده
Hetero-Diels-Alder reaction with sulfines generated in situ from methylsulfones 5a-e substituted in α-position with a phosphonyl, carboxyl, carboxyoxazolidinyl, pyridyl, or a quinolyl substituent, respectively, led to new highly functionalized thiopyrans cycloadducts. When in the substrates (i.e. 5a-c) the sulfonyl group and the second substituent on the methylene carbon have comparable electronwithdrawing effect, a mixture of cis and trans isomers of the corresponding cycloadducts is obtained with low to moderate selectivities. In the case of substrates 5d and 5e, due to the strong electronwithdrawing effect of the sulfonyl compared to the pyridyl or quinolyl groups, a single isomer is obtained for cycloadducts 7d and 7e. The stereochemical arrangements in the two cycloadducts resulting from 5b and 5d (carboxylate and pyridine derivatives) have been determined by single-crystal X-ray analysis and showed that the trans isomer was favored in both cases.
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