Catalytic Enantioselective Reaction of Allenylnitriles with Imines Using Chiral Bis(imidazoline)s Palladium(II) Pincer Complexes

Abstract

The first highly enantioselective reaction of allenylnitriles with imines has been developed. Excellent yields and enantioselectivities were observed for the reaction with various imines using chiral Phebim-Pd complexes. This process offers a simple and efficient synthetic route for various functionalized α-vinylidene-β-aminonitriles and their derivatives.

Synthesis, Characterization, and Catalytic Studies of Unsymmetrical Chiral NCC Pincer Pd(II) and Ni(II) Complexes Bearing (Imidazolinyl)aryl NHC Ligands

“…Recently, the Arai group reported nucleophilic addition of N -Boc imines under basic conditions in the presence of a chiral imidazolidine-based Pd-OTf catalyst, which gave the 3-indolyl methanamines in up to 99% yield and 98% ee . On the other hand, enantioselective aza-Morita–Baylis–Hillman (aza-MBH) reactions represent an effective strategy to prepare chiral α-methylene β-amino carbonyl compounds. , Recently, the Nakamura and Shibata group developed aza-MBH reactions of acrylonitrile and imines (up to 98% yield and 98% ee) in the presence of a chiral Phebim-Pd pincer complex . On the basis of previous literature, we herein conducted a preliminary investigation on pincer Pd complex catalyzed asymmetric aza-Friedel–Crafts reactions of indole with N-Ts imine (Scheme a).…”

Chiral Imidazoline Ligands and Their Applications in Metal‐Catalyzed Asymmetric Synthesis†

“…The four catalysts were employed in the nucleophilic addition of α ‐cyanocarbanions with imines. Utilizing benzyl nitrile, [ 100 ] acrylonitrile [ 101 ] (via aza‐Morita‐Baylis‐Hillman reaction promoted by DABCO), α ‐cyanoacetic acid [ 102 ] (via decarboxylative cyanoalkylation), α ‐aminoacetonitrile [ 103 ] (using α ‐iminonitriles), α ‐phenylthioacetonitrile, [ 104 ] α , α ‐dichloroacetonitrile [ 105 ] , α , α ‐dithioacetonitrile, [ 106 ] allenylnitrile [ 107 ] as precursors of α ‐cyanocarbanion, different α ‐substituted‐ β ‐aminonitriles could be synthesized (Scheme 47).…”

Catalytic Conversion of Nitriles by Metal Pincer Complexes

“…Scheme 34 Enantioselective Michael addition of 2-methyl-cyanoacetate catalysed by chiral pincer complexes Scheme 35 Enantioselective Michael reaction of 2-methyl-cyanoacetate and MVK catalysed by a chiral palladium pincer complex Catalytic Conversion of Nitriles by Metal Pincer Complexes cyanoacetic acid (up to 82% yield, 90% ee) [66], α-phenylthioacetonitriles [up to 99% yield, 95:5 dr (anti/syn), 99% ee (anti)] [67], α-aminoacetonitriles [up to 95% yield, 97:3 dr (syn/anti), 99% ee (syn)] [68], dichloroacetonitrile (up to 99% yield, 94% ee) [69] and allenylnitriles (up to 89% yield, 99% ee) [70]. Whereas these transformations are all Mannich-type reactions, the same catalyst has also been used for an aza-Morita-Baylis-Hillman reaction between acrylonitrile and tosylated imines (for the product, see Scheme 37, upper right).…”