Tandem chain extension–Mannich reaction: an approach to β-proline derivatives

A zinc carbenoid-initiated chain extension reaction provides access to an organometallic intermediate, which can be used to capture activated imines. Deprotection of the nitrogen and reduction provides access to racemic derivatives of β-proline. The relative stereochemistry of the β-proline can be controlled through use of different activating groups on the imine nitrogen.

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