The Co(ii)/spiroBox-catalyzed enantioselective Mukaiyama-Mannich reaction for the synthesis of quaternary α-amino acid derivatives

Abstract

Cobalt complex of chiral spiroBox ligand catalyzed Mukaiyama-Mannich reaction of enol silyl ether with cyclic N-sulfonyl ketimino ester was examined. Excellent yield (up to 99%) and ee value (up to...

Accessing unnatural α-amino acids with tetrasubstituted stereogenic centersviacatalytic enantioselective reactions of ketimine-type α-iminoesters/α-iminoamides

“…Asymmetric Mukaiyama–Mannich-type reactions of 4 with silyl enol ethers catalyzed by the combination of a nickel salt and chiral BOX ligand 6f , or a cobalt salt and chiral BOX ligand 6i , were reported by Fu in 2017 or Teng in 2022, respectively (Scheme 11, middle, bottom). 23,24 The latter report proposed a transition state involving an octahedral Co( ii ) species stabilized by π–π stacking interactions between the aromatic ring of 4 and the indane moiety of 6i . Furthermore, both reports demonstrated broad substrate scope and versatile chemical transformations involving synthesized 27 .…”

A Cu-BOX catalysed enantioselective Mukaiyama-aldol reaction with difluorinated silyl enol ethers and acylpyridine N-oxides

“…In this context, the employment of difluoroenoxysilanes 11 as nucleophiles has been demonstrated to be an efficient tool for the synthesis of difluoromethyl-containing compounds. However, the number of examples involving the nucleophilic addition of difluoroenoxysilanes in an enantioselective fashion is scarce and almost limited to nucleophilic addition to imines, 12,13 while the Mukaiyama aldol-type reaction 14 remains almost unexplored and only two organocatalytic examples involving reactive α-keto esters 15 or isatins 16 have been reported by Zhou, to the best of our knowledge (Scheme 1).…”