A Modified and Highly Useful Protocol for the Brønsted Acid Catalyzed, Enantioselective, Vinylogous Mannich Reaction with Aliphatic Aldimines

Abstract

Highly enantioselective as well as diastereoselective catalytic vinylogous Mannich reactions have been accomplished for the first time with aliphatic straight-chain aldimines and O,O-silylketene acetals and furnish valuable synthetic building blocks in high enantiomeric purity.

Key words

vinylogous Mannich reaction - phosphoric acid - organocatalyis - contact ion pair - dienolate - BINOL

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14

Enantiomeric excess was determined after reduction to the corresponding allylic alcohol with DIBAL-H (0.1 M in THF, 5 equiv) at -78 ˚C to r.t.

15

Enantiomeric excess was determined after hydrogenation and lactamization according to the synthesis of 9.