Enantioselective Hydrosilylation and Hydrogenation of Alkaloid Precursors

Abstract

AbstractEnantioselective hydrosilylations of the 3,4‐dihydropyrrole derivatives 1a–c and 5 with in‐situ catalysts consisting of [Rh(cod)Cl]2 and optically active phosphines yield the N‐silyl compounds 2a–c and 6 in up to 66.1% ee. The N‐silyl derivatives were treated with acetic formic anhydride or trifluoroacetic anhydride to give the N‐formyl and N‐trifluoroacetyl compounds 3a–c, 4a–c, 7, and 8. The alkaloids nicotine and macrostomine were synthesized with 63.3 and 33% ee by reduction of the N‐formyl compounds 8 and 12. Enantioselective hydrogenations of the N‐formyl and N‐trifluoroacetyl‐2‐phenylpyrrolines 14 and 15 with the same in‐situ catalysts produce the cyclic amides 3a and 4a in up to 36.1% ee.