Acid chlorides organocopper compounds

Ttansmetalation of tliioetliets to organocopper compounds can also be performed in some special cases. Tluis, tteatment of the ester 119 with MeyCuLi-LiCN provides the copper reagent 120, which can be treated successfully witli several electrophiles such as allyl bromide ot acid chlorides to afford the expected products such as 121 iScbeme 2.54) [115, 116]. 

Because of the toxicity of cadmium compounds two alternative methods for the preparation of ketones from carboxylic acid derivatives are worthy of attention. The first involves the reaction of organocopper reagents [formed from copper(i) iodide and an alkyllithium] with a carboxylic acid chloride.12 7a,b... 

You met organocopper reagents in Chapter 10 where you saw that they did conjugate additions to a,p-unsaturated carbonyl compounds. Other metals, such as cadmium or manganese, can also be used to make ketones from acid chlorides. 

Ultraviolet spectral data have been reported for a few organocopper compounds 36, 77, 253, 303). Methyl(triphenylphosphine)copper complexes were decomposed by UV light 310). The reaction of Grignard reagents with acid chlorides in the presence of copper(I) chloride, in which free radicals are supposedly formed via organocopper compounds, was also promoted by UV light 103). 

However, good yields of ketones can be obtained for an equivalent quantity of acid halide per group attached to copper. Suitable conditions exist for the coupling of dialkylcuprates with acid chlorides which contain other functional groups (233), such as carbonyl, carboxy, and cyano. The order of reactivity of these groups towards organocopper compounds is CHO > CO > COgR > CN. Benzoyl fluoride reacts very slowly with lithium dimethylcuprate. 

We have found that alkynylsilanes are smoothly converted into alkynylcopper compounds by treatment with CuCl in l,3-dimethyl-2-imidazohdinone (DMI) the copper reagents can be isolated in good yields [563]. This study was the first example of preparation and isolation of organocopper compounds by use of organosilicon reagents. The Si-Cu transmetalation is applicable to the synthesis of alkynyl ketones by Cu-catalyzed alkynylation of acid chlorides (Scheme 10.217). We have also shown that a Cu-mediated system is effective in the cross-coupling reaction between arylsilanes or heteroarylsilanes and aryl hahdes [564]. 

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