Applications of chiral N-sulfinylcarbamates in asymmetric synthetic methodologies
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Abstract
Using (R)-8-phenylmenthol and trans-2-phenyl-cyclohexanol as chiral auxiliaries, the stereoselectivities of the [4+2] cycloaddition and the ene reactions of their respective N-sulfinylcarbamates are explored. In the presence of a Lewis acid, the cycloadditions exhibit inductions greater than 95:5 with the former of these two sources of chirality, affording dihydrothiazine 1-oxides which have been extensively elaborated to chemically useful and important synthons. The ene reactions with a Lewis acid present are also highly stereoselective, yielding the N-(alkoxycarbonyl)-allylicsulfinamides of which a useful transformation is developed and reported here. The net effect of this transformation is a regio- and and stereoselective allylic oxidation of an unactivated alkene with complete reagent control of the absolute stereochemistry. The significance of this chemistry is clearly illustrated by the synthesis of an intermediate towards PGF₂[subscript alpha] where a remote stereocenter is enantioselectively introduced