Vinylic cyanocuprates

The conjugate addition of higher-order (Z)-vinylic cyanocuprates, to enones,has been submitted to further useful modifications. Thus it was shown that the serious drawback of this methodology, which is the inertness of hindered enones to the mentioned reagents when THF is used as solvent, can be overcome by the addition of BFj etherate to the reaction mixture, or simply by performing the reaction in ether in the presence or absence of... 

The (Z)-vinylic cyanocuprates also react with epoxides (e.g., 198) giving the (Z)-homoallylic alcohols (e.g., 199).41,270 The reaction is stereospecific and offers the possibility of its application in enantioselective synthesis (Scheme 109). 

Keeping in mind the easy access to vinylic tellurides (see Sections 5.2.3 and 5.2.5), and their fast transformation into widely-used reactive organometallics, we can consider this reaction sequence as a valid alternative to the known methods of generating vinyllithiums and, specially, vinyl cyanocuprates. In addition, the zz/r/r-hydrotel I u ration of alkynes is unique among the known, synthetically useful hydrometallations, since it allows the direct preparation of... 

Recently, this unique characteristic of vinylic tellurides was explored in the enantioselective synthesis of macro-lactin A 205, an antiviral macrolactone extracted from sea bacteria. The first step of the synthesis featured the chiral epoxide 203 opening by the vinyl cyanocuprate 202, derived from a tellurium-copper exchange reaction using the vinylic telluride 201, obtained by hydrotelluration of 200 (Scheme 111). Further manipulation of 204 led to macrolactin A 205.271... 

Vinylic cyanocuprates, prepared from vinylic tellurides, react with bromoalkynes giving conjugated (Z)-enynes and (Z)-enediynes." ... 

Novel organocuprates used in conjugate additions are 2-(trimethylgermyl)allylcopper(I) [MejS complex], dilithium bis[2-trimethylstannyl)vinyl]cyanocuprate, and the a-azoalkylcuprates. ... 

---