Synthesis and evaluation of the catalytic properties of semicarbazides derived from N-triphenylmethyl-aziridine-2-carbohydrazides

A straightforward synthesis of a series of new catalysts derived from N-triphenylmethyl-aziridine-2-carbohydrazides is described. The new compounds have been tested for the enantioselective addition of diethyl- and phenylethynylzinc to aryl and alkyl aldehydes, which afforded the corresponding chiral alcohols in high chemical yields (up to 92%) and with excellent ee’s of approximately 90%.

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(2S)-1-Tritylaziridine-2-carbohydrazideC22H21N3Oee = 99%[α]Drt=-16.0 (c 1, CHCl3)Source of chirality: l-serineAbsolute configuration: (S)

1-Butyl-3-[[(2S)-1-tritylaziridine-2-carbonyl]amino]ureaC27H30N4O2ee = 99%[α]Drt=-12.0 (c 1, CHCl3)Source of chirality: l-serineAbsolute configuration: (S)

1-tert-Butyl-3-[[(2S)-1-tritylaziridine-2-carbonyl]amino]ureaC27H30N4O2ee = 99%[α]Drt=-20.0 (c 1, CHCl3)Source of chirality: l-serineAbsolute configuration: (S)

1-Cyclohexyl-3-[[(2S)-1-tritylaziridine-2-carbonyl]amino]ureaC29H32N4O2ee = 99%[α]Drt=-12.0 (c 1, CHCl3)Source of chirality: l-serineAbsolute configuration: (S)