Zinc-copper couple carbonyl compounds

In similar work, CF3CCI2CO2CH3 yields methyl a-trifluoromethyl-a,(i-un-saturated carboxylates when reacted with a zinc-copper couple, aldehydes, and acetic anhydride [67] (equation 55). This methodology gives (Z)-a-fluoro-a- -un-saturated carboxylates from the reaction of carbonyl compounds with CFCI2CO2CH3 and zinc and acetic anhydride [6 ]. 

Luche reported that when a zinc-copper couple was used, alkyl halides reacted with conjugated carbonyl compounds and nitriles to give 1,4-addition products in good yields under sonication conditions (Eq. 10.26).57... 

A convenient method for the conversion of aldehydes (RCHO) to alkenes (RCH = CHj), knovm as methylenation, involves the reaction of a zinc/copper couple with diiodomethane in the presence of the carbonyl compound dissolved in tetrahy-drofuran. The reaction first generates an organometallic intermediate (ICH2ZnI) which then reacts with the carbonyl compound. The conversion of benzaldehyde to styrene using this conventional methodology required a reaction time of 6 h at 40 °C. When the reaction was sonicated however comparable yields of around 70%... 

Phosphomolybdic acid-Potassium di-chromate-Copper(II) sulfate, 248 Tin(II) trifluoromethanesulfonate, 301 Other unsaturated carbonyl compounds Lead tetraacetate, 155 Pyrylium perchlorate, 263 Zinc-copper couple, 348 a-Substituted-a, p-unsaturated carbonyl compounds... 

For many years the elucidation of the mechanism of the McMurry reaction has been complicated by the fact that the most commonly used low-valent titanium was derived from hour-long pre-reducing DME-complexed TiCl3 with a zinc/copper couple (DME is 1,2-dimethoxyethane). Apparently, however, the zinc/copper couple reacts with TiCl3 only if the carbonyl compound is present, too. This fact has become part of the current mechanistic view of the McMurry reaction (Figure 17.58). At the same time, it became the starting point of the following variants of the McMurry reaction ... 

Reactions of this type have been reported tor reactions of a,a -dibromoketones with iron carbonyl compounds or zinc-copper couple as catalysts (4, 157-158 5, 221-224). 

The reaction of phosphorus ylides with carbonyl compounds as a route to fluoro-olefins is prone to complications (see Vol. 2, p. 46), but excellent yields of olefins are obtained upon dehalogenation of fluoroiodomethyltriphenylphos-phonium iodide with zinc-copper couple, e.g, ... 

Ishihara and coworkers have reported that the reaction of 2-[(trimethylsilyl)methyl]-3-chloro-3,3-difluoropropene couples regioselectively with a variety of carbonyl compounds in the presence of zinc-copper chloride or silver acetate to give 2,2-difluoro-3-(trimethylsilyl)methyl-3-buten-l-ol derivatives (equation 87)81. Note again that the difluo-roallyl zinc species generated in situ reacts exclusively on the difluoromethylene terminus. 

Indium mediated Barbier-type cross coupling between carbonyl compounds and allyl halides proceed efficiently under solvent-free conditions. No apparent competing pinacol-coupling or homo-coupling of the allyl halide was observed. The reactions were found to be mediated also by zinc, tin, bismut and copper [45]. 

Aldol synthesis. A new synthesis of 3-hydroxy ketones and esters involves regiospecific conversion of an a-bromo ketone or ester into an aluminum enolate by a coupled reaction with diethylaluminum chloride and zinc activated with copper(I) bromide in THF at —20°. This enolate adds to carbonyl compounds to give, after work-up, j3-hydroxy ketones (equation I). 

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