Reformatsky reactions with indium compounds

Table 9. Summary of reformatsky reaction of carbonyl compounds with activated indium and ethyl bromoacetate1)...

The activated indium can be used to effect the Reformatsky reaction of carbonyl compounds with ethyl bromoacetate. High yields can be realized when an excess of the carbonyl compound is used. ... 

Application of zinc as a sacrificial anode often overcomes the difficulties with activation of zinc in the Reformatsky reaction and the problems with uncontrolled exothermic reactions. When zinc or indium is employed for the reaction, the amount of electricity used is less than the theoretical, and this suggests that the anode acts as activated metal and reacts with the bromo compound [175]. 

Reformatsky-type reaction. Bromoacetonitrile reacts rapidly with indium and subsequent treatment with carbonyl compounds leads to /3-hydroxy nitriles. 

Reformatsky-type reaction. Using indium and iodine in DMF, the condensation of phenyl a-bromoalkanoates with carbonyl compounds leads to p-lactones. 

A one-pot preparation of 4-iodomethyloxetan-2-one is reported (93SL899). Electrochemically generated organometallic compounds react with ketones in a Reformatsky reaction to give esters or lactones (93AG1218) and the formation of P-lactones is favoured when a sacrificial indium anode is used (94JOC3161). 

The reaction of an a-halo carbonyl compound with zinc, tin, or indium together with an aldehyde in water gave a direct cross-aldol reaction product (Eq. 8.90).226,227 A direct Reformatsky-type reaction occurred when an aromatic aldehyde reacted with an a-bromo ester in water mediated by zinc in low yields. Recently, it was found that such a reaction mediated by indium was successful and was promoted by son-ication (Eq. 8.91).228 The combination of BiCl3-Al,229 CdCl2-Sm,230 and Zn-Et3B-Eb0231 is also an effective mediator. Bismuth metal, upon activation by zinc fluoride, effected the crossed aldol reaction between a-bromo carbonyl compounds and aldehydes in aqueous media. The reaction was found to be regiospecific and syn-diastereoselective (Eq. 8.92).232... 

Aqueous Reformatsky-type cross-coupling reactions have also been reported (Chan et al., 1990,1994). Metallic zinc, tin or indium promote the aldol-type condensation of a-halocarbonyl compounds and aldehydes in aqueous media (Scheme 4.11). Likewise, a-haloesters (a-haloacids) were allowed to react with aromatic aldehydes to provide p-hydroxyesters (P-hydroxyacids) in moderate yields (Chan et al., 1994). 

---