Conjugate addition of organocopper reagents

CONJUGATE ADDITION OF ORGANOCOPPER REAGENTS TO a,p-UNSATURATED CARBONYL COMPOUNDS... 

Conjugate additions to enals and enones.1 ClSi(CH,)3/HMPT markedly accelerates the Cu(I)-catalyzed conjugate addition of Grignard reagents to enals, enones, and unsaturated esters. The conjugate addition of organocopper reagents is also facilitated. 

Tab. 6.1. Results of conjugate addition of organocopper reagents to enones 20 and 21.

Conjugate addition of organocopper reagents has also been used to introduce multifunctional groups in the final carbon-carbon bond-forming step. The immunosuppressant FK-506 (25) [17] was noteworthy in its activity, which was found... 

Etiolates 5 and 7, generated regiospecifically by conjugate addition of organocopper reagents to 2-cyclopentenones, can also be stereoselectively alkylated49,50. 

The products are useful substrates for conjugate addition of organocopper reagents (see this volume). 

The conjugate addition of organocopper reagents to polyalkenic carbonyl compounds presents an opportunity in which either 1,4-, 1,6- and sometimes 1,8-addition can occur. Much of the early woik in this area was conducted in the study of the reaction of a dienoate or dienone with an alkylcuprate or a catalytic copper/organomagnesium combination. The predominant mode of addition for the reaction of a dienoate and a copper-based organomagnesium reagent was found to be 1,6 not 1,4.72 If the opportunity of 1,8-addition was present, then this mode prevailed.73 However, a truly systematic study has not been carried out with the various reagents. 

The conjugate addition of organocopper reagents to ot,(3-alkynic esters, ketones, aldehydes and acids is a useful method for the preparation of various tri- and tetra-substituted alkenes,87 although addition to aldehydes is less common.88 Use of a vinylcuprate results in the formation of a conjugated dienone, which further highlights the importance of this methodology (equation 43 ).87... 

The stereo- and regio-selective conjugate addition of organocopper reagents to various enones has been reported.144-146 Models accounting for the stereochemical outcome have been presented. 

Bellosta, V, Czernecki, S, C-glycosyl compounds. IV. Synthesis of (2-deoxy-a-D-glyc-2-enopyr-anosyl)arenes by stereospecific conjugate addition of organocopper reagents to peracetylated hex-1-enopyran-3-uloses, Carbohydr. Res., 171, 279-288, 1987. 

A synthesis of a-substituted S-unsaturated acids exploits the facile Claisen rearrangement of allyl ester enolates, which can be generated by conjugate addition of organocopper reagents to ally 2-alkenoates. ... 

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