Coordination and derivatization of 3, 4, and 6-membered nitrogen heterocycles at a chiral tungsten(II) center

摘要

Reaction of [Tp'W(CO)(2)(PhC CPh)][OTf] (1b) (Tp' = hydridotris(3,5-dimethylpyrazolyl)borate) with excess aziridine or 2-methylaziridine followed by protonation with HdOEt(2))(2)][BAr'(4)] produces chiral tungsten(II) amine complexes [Tp'W(CO)-(PhC CPh)(NHCH2CHR)][BAr'(4)](3, 4; R = Me, Ph). An azetidine amido complex, Tp'W(CO)(PhC CMe)(NCH2CH2CH2) (5) is synthesized by reaction of [Tp'W(CO)(2)(PhC CMe)][OTf] (1a) with excess azetidine. Oxidation of amido complex 5 with I-2 in the presence of a weak base provides the corresponding 1-azetine complex, Tp'W(CO)(PhC CMe)(N=CHCH2CH2)][BAr'(4)] (6). Addition of methylmagnesium bromide to complex 6 results in formation of predominantly one diastereomer (SWRC/RWSC) (96:4 dr) of the 2-methylazetidine complex, Tp'W(CO)(PhC CMe)(NCHMeCH2CH2) (7). Reaction of complex 5 with H('OEt2)(2)][BAr'(4)] results in formation of a cationic azetidine complex, Tp'W(CO)(PhC CMe)(NHCH2CH2CH2)(BAr'(4)) (8). Reaction of 1b with excess piperidine followed by oxidation affords 2,3,4,5-tetrahydropyridine complex 9b, Tp'W(CO)(PhC CPh)(N=CHCH2CH2CH2CH2))][BAr'(4)]. Formation of an enamido complex, Tp'W(CO)(PhC CPh)(NCH=CHCH2CH2CH2) (10), is observed upon addition of base to 9b. Subsequent addition of [D+] to the enamido b-carbon results in the formation of the deuterated product, 9b-d(1), as determined by H-2 NMR. Seven X-ray crystal structures have been determined, and these encompass complexes with 3, 4, and 6-membered heterocyclic ligands. Crystal structures are reported for two aziridine adducts (2, 4) two neutral amido complexes (5, 7), one cationic imine complex (6), and one cationic amine (8) complex derived from azetidine, and the imine complex formed from piperidine (9). (c) 2007 Elsevier B.V. All rights reserved.