Vinyl epoxides acylic compounds

Lithiation of compound 560 with s-BuLi-TMEDA in THF at —78 °C following an inverse addition protocol provided the anion 561. It reacts with primary alkyl iodides and triflates, silyl chlorides, diphenyl disulfide, epoxides, aldehydes, ketones, imines, acyl chlorides, isocyanates and sulfonyl fluorides to yield the expected compounds 562 (Scheme 152). The transmetallation of compound 561 with ZnBr2 allowed the palladium-catalyzed cross-coupling reaction with aryl and vinyl bromides837. When the reaction was quenched with 1,2-dibromotetrafluoroethane, the corresponding bromide 562 (X = Br) is obtained838. 

The scope of vinyl metals as sources of nucleophilic vinyl groups is very great. As well as the expected electrophiles such as halogens, alkyl and acyl halides, aldehydes and ketones, unsaturated carbonyl compounds and epoxides, they also combine with aryl and alkenyl halides with palladium catalysis. The usual stereochemical course is retention at the vinyl group. It is necessary to decide whether the vinyl metal is reactive enough or whether it must first be transformed into an ate complex. Since most of these vinyl metals can be converted into each other with retention, this is an unusually versatile group of reagents. 

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