Zhang X, Staples R, Rheingold AL, Wulff WD. Catalytic asymmetric α-Iminol rearrangement: new chiral platforms.
J Am Chem Soc 2014;
136:13971-4. [PMID:
25247674 PMCID:
PMC4195388 DOI:
10.1021/ja5065685]
[Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Indexed: 11/29/2022]
Abstract
A series of 19 different asymmetric catalysts were screened in an effort to identify the first chiral catalyst for the rearrangement of α-hydroxy imines to α-amino ketones involving a 1,2-carbon shift. Although aluminate complexes of VAPOL, VANOL, and 7,7'-(t)Bu2VANOL were quite effective catalysts giving up to 88% ee, the ne plus ultra catalyst for this reaction was found to be a zirconium complex of VANOL which gives 97 to >99% ee for the majority of the substrates examined. An X-ray diffraction study of the catalyst reveals that the zirconium exists as a homoleptic complex with three VANOL ligands and two protonated N-methyl imidazoles.
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