Alkyne-stabilized monomeric organcopper(I) compounds as organyl transfer reagents

The reaction chemistry of the monomeric organo-copper(I) species ([Ti](C dr op CR1)(2))CuR ([Ti] = (eta (5)-C5H4SiMe3)(2)Ti; R-1 = SiMe3: 1a, R=CH3; 1b , R=C6H5; 1c, R=C6H4OMe-4; 1d, R=C dropC'Bu; 1e, R= C drop CSiMe3; R-1 ='Bu : 8a, R=C drop CSiMe3; 8b, R = CH3) towards different inorganic and organic reagents is described. On treatment of 1a-1e with one equivalent of X-2 (2a: X = Br, 2b: X = I) se lective cleavage of the copper-carbon sigma -bond is observed, producing ([ Ti](C drop CSiMe3)(2))CuX (4a: X = Br, 4b: X = I) along with R-X (X = Br: 3 a, R = CH3; 3b, R = C6H5; 3c, R=C6H4OMe-4; 3d, R=C-C'Bu; 3e, R=C drop CSiMe 3; X=I: 3f, R=C drop CSiMe3; 3g, R=C dropC'Bu). Treatment of ([Ti](C drop C SiMe3)(2)) CuC drop CR3 (Id: R-3 = 'Bu, 1e: R-3 = SiMe3) with ICN (7) produ ces ([Ti](C dropC'Bu)(2))CuCN (9) and 3f or 3g. Copper-carbon sigma -bond c leavage is also obtained, when la or 8b is treated with stoichiometric amou nts of HX (10a: X = Br, 10b: X = Cl), NH4Cl or NEt3HCl. In contrast, a carbon-carbon coupling is observed when ([Ti](C drop CR1)(2) )CuR (1, 8) is reacted with R-2-X (R-2 = CH3, CH2CH3, CH2C6H5, C drop CSiMe 3; X = Cl, Br, I) in a 1:1 molar ratio. This yields R-2-R and ([Ti](C drop CR1)(2))CuX (R-1 = SiMe3: 4a, X = Br: 4b: X = I; 4c: X = Cl; R-1 ='Bu: 11a: X = Cl; 11b: X = Br, 11c: X = I). The latter molecules can be transformed into the corresponding starting materials 1 or 8 by their reaction with, e. g., LiR (5). However, when aromatic halides, such as IC6H4Me-4, are added t o ([Ti](C drop CSiMe3)(2))CuC drop CR3 (1d: R-3 = 'Bu, 1e: R-3 = SiMe3), el imination of Me3SiC drop CR3 takes place and the titanium(IV)-copper(I) ace tylide ([Ti](C drop CSiMe3)(C drop CCu))(2) (15) is formed. In addition, organo copper(I) compounds can be considered as key molecules in the decarboxylative bromination of copper(I) carboxylates: heating the c opper(I)-carboxylate ([Ti](C drop CSiMe3)(2))CuO2CR2 (6a: R-2 = CH3, 6b: R- 2 = C6H5) to 100 degreesC produces the organo copper(I) species 1a and 1b b y loss of CO2. On treatment of 1a and 1b with equimolar amounts of Br-2, ox idative cleavage of the Cu-C sigma -bond is induced and ([Ti](C drop CSiMe3 )(2))CuBr (4a) as well as R-2-Br are formed. Complex 4a can be transformed to the starting material 6a or 6b by subsequent reaction with AgO2CR2 (R-2 = CH3, C6H5) on precipitation of AgBr. All compounds synthesized were characterized by elemental analysis and spec troscopy (IR,H-1-NMR, C-13(H-1)-NMR). The organic products were characteriz ed additionally by GC-mass spectrometry. (C) 2001 Elsevier Science B.V. All rights reserved.