Pyrrolidines have numerous applications such as pharmaceuticals, agrochemicals and as catalysts. The [3+2] cycloadditions of azomethine ylides are perhaps the most elegant and efficient methods of pyrrolidine synthesis possessing the potential of forming four stereocentres in a single step. Previous protocols for the asymmetric [3+2] cycloadditions suffer the necessary moieties on the ylide for chelation. These groups are then present in the product, making the synthesis of pyrrolidines, unsubstituted in the 2-and 5-positions, impossible by these methods. Our approach aims to use a cheap, readily available chiral auxiliary on the nitrogen of the azomethine ylide to install stereocentres selectively at the 3- and 4- positions. The more favourable exo- transition state, results in moieties on the dipolarophile being in the proximity of the chiral auxiliary, making chiral induction possible, as demonstrated by previous groups. Sulfinamides are currently under investigation, partly due to the ease of cleavage of the N-S bond, but more importantly, the high polarity of the auxiliary is expected to result in a more rigid transition state compared to previous chiral auxiliaries.

Asymmetric [3+2] cycloadditions of azomethine ylides generated from chiral sulfinamide precursors

255th National Meeting (2018)

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