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Title: Diastereo- and Enantioselective Iridium Catalyzed Coupling of Vinyl Aziridines with Alcohols: Site-Selective Modification of Unprotected Diols and Synthesis of Substituted Piperidines. Author: Wang G, Franke J, Ngo CQ, Krische MJ. Journal: J Am Chem Soc; 2015 Jun 24; 137(24):7915-20. PubMed ID: 26074091. Abstract: The chiral cyclometalated π-allyliridium ortho-C,O-benzoate complex (R)-Ir-VIb derived from [Ir(cod)Cl]2, allyl acetate, 4-cyano-3-nitro-benzoic acid, and (R)-MeO-BIPHEP catalyzes the coupling of N-(p-nitrophenylsulfonyl) protected vinyl aziridine 3a with primary alcohols 1a-1l to furnish branched products of C-C bond formation 4a-4l with good levels of anti-diastereo- and enantioselectivity. In the presence of 2-propanol, but under otherwise identical conditions, vinyl aziridine 3a and aldehydes 2a-2l engage in reductive coupling to furnish an equivalent set of adducts 4a-4l with roughly equivalent levels of anti-diastereo- and enantioselectivity. Using enantiomeric iridium catalysts, vinyl aziridine 3a reacts with unprotected chiral 1,3-diols 1m-1o in a site-selective manner to deliver the diastereomeric products of C-allylation syn-4m, -4n, -4o and anti-4m, -4n, -4o, respectively, with good isolated yields and excellent levels of catalyst-directed diastereoselectivity. These adducts were directly converted to the diastereomeric 2,4,5-trisubstituted piperidines syn-5m, -5n, -5o and anti-5m, -5n, -5o.[Abstract] [Full Text] [Related] [New Search]