Lithiated gamma-tosyl-substituted benzylmethallylamine: New gamma-amino methallyl sulfone anions in organic synthesis

The mono- and dilithiation of benzyl[2-(tosylmethyl)-2-propenyl]amine (9) with n-butyllithium at -78 degrees C leads to the new allyl sulfone monoanion 10a and dianion 10b, respectively. The intermediate 10a reacts regioselectively at the alpha-position with respect to the sulfone group with different electrophilic reagents (deuterium oxide, alkyl halides, propanal, phenyl isocyanate, and electrophilic olefins) to give the corresponding derivatives 11. In the case of ethyl propiolate, double Michael addition took place, and the trans-substituted methylenepyrrolidine 13 was stereoselectively obtained. Dianion 10b also reacts at the nitrogen atom when alkyl halides and ethyl propiolate are used as electrophiles. These intermediates 10 are appropriate dinucleophiles in annelation reactions with dielectrophiles to afford six-, seven-, and eight-membered ring nitrogen heterocycles 20. When 1,3-dichloroacetone, (Z)-1,4-dichloro-2-butene, and epibromohydrin were used as electrophiles the cyclization process was stereoselective. Studies on the configuration and conformation of prepared heterocycles 20 have been carried out by means of H-1 NMR experiments and X-ray analysis, which have been confirmed by Molecular Mechanics calculations. Base-induced dehydrosulfinylation, reductive desulfonylation, and methylenation reactions have been studied with representative derivatives.