Cyanohydrins, Reformatsky reactions

A second example is the intermolecular reaction of an ethyl a-bromo-a-fluoro-or trifluoromethylacetate (Eq. 77). With TMS-protected cyanohydrins, the Reformatsky reaction yields p-keto-y-butyrolactones. Sonication is essential for success. 

The reaction of a nitrile with a Reformatsky reagent is known as the Blaise reaction and when applied to (9-trimethylsilyl cyanohydrins leads to the formation of tetronic acids with high ee [79]. By working-up the Blaise reaction with ammonium chloride it is possible to isolate... 

Tetronic acids and P-keto-y-butyrolactones are easily prepared by reaction of an 0-trimethylsilylated cyanohydrin with a-bromo esters in the presence of a Zn- u couple in a Reformatsky-type reaction (Scheme 12). ... 

Keto-y-butyrolactones teironic acids Zinc, activated with Cu(OAc)2, promotes a Reformatsky-type reaction of a-bromo esters with O-silylated cyanohydrins to provide p-keto-y-butyrolactones or tetronic acids. 

A partial reduction of O-protected chiral cyanohydrins is also possible by reaction with Reformatsky reagents (Blaise reaction). The primarily formed imino intermediates can be hydrolyzed under very mild conditions to give the enamines ( )-15, which yield by treatment with strong acids the tetronic acids (R)-16 (Scheme 9) [39,40]. 

---