Reformatsky reactions alternative metals

Bieber reported that the reaction of bromoacetates is greatly enhanced by catalytic amounts of benzoyl peroxide or peracids and gives satisfactory yields with aromatic aldehydes. A radical chain mechanism, initiated by electron abstraction from the organometallic Reformatsky reagent, is proposed (Scheme 8.27).233 However, an alternative process of reacting aldehydes with 2,3-dichloro-l-propene and indium in water followed by ozonolysis provided the Reformatsky product in practical yields.234 An electrochemical Reformatsky reaction in an aqueous medium and in the absence of metal mediator has also been reported.235... 

An alternative strategy to improve the efficiency of Reformatsky reactions makes use of freshly prepared metal couples, particularly the Zn—Cu couple32 and the Zn—Ag couple33 in TFIF as solvent. 

B. Addition to Carbonyl Compounds - Addition of metalated carboxylic acids to aldehydes and ketones affords a useful and versatile alternative to the Reformatsky reaction.42 The reaction is sensitive to steric effects... 

Bioactive compounds that contain the difluoromethylene group adjacent to the carbonyl functionality have been the subject of increased research efforts in recent yearsf 59). The most widely utilized methods that have been employed to introduce this group into organic molecules have been (a) Reformatsky reaction of halodifluoroacetates (60-66) (b) elaboration of difluoroketene silyl acetals (67-69) (c) metal catalyzed addition of 3-bromo-3,3-difluoropropene to aldehydes and ketones (70) and (d) alkylation of CuCF2COOR(77). The modest yields associated with these methods prompted us to explore alternative methodology for the preparation of this useful building block. 

Reformatsky reaction. As an alternative promoter to zinc metal, the use of Mg-FeCls or Mg-CuCl2 2H2O has been demonstrated. 

The more than 125-year-old Reformatsky reaction of aldehydes or ketones with a-haloesters is a valuable alternative to the aldol reaction leading also to P-hydroxycarboxylic esters [158]. In its classic version, the reaction occurs through zinc enolates, but not only zinc can serve as a mediator but also various other metals in low oxidation stage like titanium, indium, and samarium. In... 

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