Enantioselective Hydrosilylation and Hydrogenation of Alkaloid Precursors

Enantioselective 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.