Fager DC, Morrison RJ, Hoveyda AH. Regio- and Enantioselective Synthesis of Trifluoromethyl-Substituted Homoallylic α-Tertiary NH
2 -Amines by Reactions Facilitated by a Threonine-Based Boron-Containing Catalyst.
Angew Chem Int Ed Engl 2020;
59:11448-11455. [PMID:
32219997 DOI:
10.1002/anie.202001184]
[Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 03/25/2020] [Indexed: 12/20/2022]
Abstract
A method for catalytic regio- and enantioselective synthesis of trifluoromethyl-substituted and aryl-, heteroaryl-, alkenyl-, and alkynyl-substituted homoallylic α-tertiary NH2 -amines is introduced. Easy-to-synthesize and robust N-silyl ketimines are converted to NH-ketimines in situ, which then react with a Z-allyl boronate. Transformations are promoted by a readily accessible l-threonine-derived aminophenol-based boryl catalyst, affording the desired products in up to 91 % yield, >98:2 α:γ selectivity, >98:2 Z:E selectivity, and >99:1 enantiomeric ratio. A commercially available aminophenol may be used, and allyl boronates, which may contain an alkyl-, a chloro-, or a bromo-substituted Z-alkene, can either be purchased or prepared by catalytic stereoretentive cross-metathesis. What is more, Z-trisubstituted allyl boronates may be used. Various chemo-, regio-, and diastereoselective transformations of the α-tertiary homoallylic NH2 -amine products highlight the utility of the approach; this includes diastereo- and regioselective epoxide formation/trichloroacetic acid cleavage to generate differentiated diol derivatives.
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