Developing a diastereoselective intramolecular [4 + 3] cycloaddition of nitrogen-stabilized oxyallyl cations derived from N-sulfonyl-substituted allenamides
Efforts toward achieving a practical and diastereoselective intramolecular [4 + 3] cycloaddition of nitrogen-stabilized oxyallyl cations with tethered dienes are described. Epoxidation of N-sulfonyl substituted allenamides with dimethyldioxirane (DMDO) generates nitrogen-stabilized oxyallyl cations that readily undergo stereoselective [4 + 3] cycloaddition with dienes. Selectivity is found to depend on the tethering length as well as the stability of the oxyallyl cation intermediate, whether generated from N-carbamoyl- or N-sulfonyl-substituted allenamides. The use of chiral N-sulfonyl-substituted allenamides provided minimal diastereoselectivity in the cycloaddition, while high diastereoselectivity can be achieved with a stereocenter present on the tether. These studies provide further support for the synthetic utility of allenamides.
Lohse, Andrew G.,Hsung, Richard P.,Leider, Mitchell D.,Ghosh, Sunil K.
experimental part
p. 3246 - 3257
(2011/07/09)
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