Cross-coupling reactions hydrometalation

In the last section, the access to a-selanyl vinylmetals is considered. Besides the classical methods involving vinylic selenides and ketene selenoacetals, the hydrometallation (M = Sn, Zr, B) of acetylenic selenides constitutes an efficient method. These species can be considered as vinyl dianion equivalents. Some examples of cross-coupling reactions are presented. 

Hydrozincation is not as widely observable as that involving , A1 and Zr. This is one of the main reasons why the indirect hydrometallation-transmetallation procedures shown in Schemes 8 and 12 have been developed and used. It is nevertheless highly desirable to directly generate organozincs to be used for the Pd- or Ni-catalyzed cross-coupling from alkenes and alkynes via hydrozincation. Indeed, such reactions have been developed, as shown in Scheme 17. However, further developments are clearly desirable. 

Hydrometallation-cross-coupling and carbometallation-cross-coupling tandem protocols and other alkenyl-aryl, alkenyl-alkenyl, and alkenyl-alkynyl coupling reactions double metal catalysis... 

Hydrometalation of alkynes is one of the most direct and powerful synthetic tools for the formation of alkenyl metal species, which could be simply hydrolyzed to yield the corresponding alkenes or readily utilized as building blocks for further transformations such as cross coupling and electrophilic substitution reactions. 

---