An NMR investigation of the reaction between cinnamic acid esters and lithium dimethylcuprate. Initial formation of an olefin-copper π-complex

A remarkably stable copper(I) ethylene complex: synthesis, spectroscopy and structure

“…Copper-catalyzed addition of carbanions to a,b-unsaturated carbonyls and coppercatalyzed cyclopropanation of alkenes by a-carbonyl diazoalkanes involve copper olefin complexes as catalytically active species or resting states. [1][2][3][4] Ethylene, the smallest plant hormone, binds tightly to the copper receptor site ETR 1, 5,6 participating in a variety of stress responses and developmental processes. 7 Thompson et al synthesized and characterized the first stable copper(i) ethylene complex, [HB(3,5-Me 2 -1,2-HC 3 N 2 ) 3 -k 3 N]Cu(h 2 -C 2 H 4 ), in 1983.…”

“…Colorless crystals, mp 108 °C (slow gas evolution and decomp. of the colorless liquid); IR (KBr/cm 21 ): n 1516 (CNC); 1 H NMR (298 K, C 6 D 6 , 300.13 MHz): d 3.48 (s + sat, 1 J CH 158 Hz, CH 2 ; 4H), 1.21 [d + sat, 3 J PH 14 Hz, 1 J CH 126.5 Hz, C(CH 3 ) 3 ; 18H], 0.21 [s + sat, 1 J CH 117 Hz, Si(CH 3 ) 3 ; 18H]; 13 C NMR (gated decoupling) (298 K, C 6 D 6 , 75.47 MHz): d 73.0 (t, 1 J CH 158 Hz, 2 J CH 4 Hz, CH 2 ), 37.2 [ddez, 1 J CP 64 Hz, 2 J CH 4 Hz, C(CH 3 ) 3 ], 28.2 [q sept d, 1 J CH 126.5 Hz, 3 J CH 5.1 Hz, 2 J CP 2.6 Hz, C(CH 3 ) 3 ], 5.6 [q'oct' + sat, 1 J CSi 57 Hz, 3 J CH ≈ 2 Hz ≈ 3 J PC , Si(CH 3 ) 3 ]; 29 Si{ 1 ‡ Data were collected on a Bruker SMART CCD instrument and the structure solutions were performed using SHELXTL V5.10, 17 respectively. Intensities were corrected for Lorentz and polarization effects, an empirical absorption correction was applied using SADABS 18 based on the Laue symmetry of the reciprocal space.…”

2.06 Formation of Enolates

“…Now it seems to be certain that the first intermediate between the α,β-unsaturated carbonyl and the cuprate is a d,p à -complex (10), and this is followed by a copper(III) β-adduct (11). [172][173][174] An authentic copper enolate can be prepared by an alternative route, which involves the conjugate addition of BuCu(BF 3 ). 175 Experimental results indicate clearly that the intermediate is a copper-bonded enolate (12) rather than an α-cupriocarbonyl derivative (13).…”

Applications of organocopper reagents in organic synthesis

“…In this paper I have deliberately concentrated on synthetic applications of organocopper reagents and refrained from any mention of reaction mechanisms. Phis is for the simple reason that, although a great deal of valuable information has been gathered (Corey & Boaz 1985;Hallnemo et al 1985;Ashby et al 1982;Krauss & Smith 19 reaction mechanisms are still not completely understood. I hope, however, that I have illustrated the potential of organocopper reagents in organic synthesis and persuaded at least some of the audience that these versatile reagents would be of use in their own research work.…”