Electrophiles organozinc reactivity

Due to the low reactivity of alkyl and arylorganozinc reagents towards alkenes and alkynes, it appears clear that the carbozincation chemistry for this class of reagents is intimately associated with transition metal catalysts. Some of the metal-catalyzed/promoted reactions do indeed produce organozinc reagents as the final organometallic species that can further react with an appropriate electrophile, whereas other processes lead to highly functionalized products by an entirely different pathway. 

Whereas uncatalyzed substitution reactions of organozinc compounds are limited to very reactive electrophiles, metal-transmetallated organozinc compounds are able to perform substitution reactions on various electrophiles. In the case of conjugated electrophiles, these zinc copper reagents can follow a Sn2 or Sn2 mechanism. 

Zinc enamides such as 50 are reactive organozinc species, which can undergo addition to unactivated olefins with good to excellent yields. After trapping of the organozinc intermediate 51 with an electrophile and hydrolysis, a variety of functionalized primary, secondary, and tertiary a-alkylated ketones are isolated (Equation (100)).170... 

The use of transition metal catalysts, especially those containing Pd and Ni, has converted otherwise unreactive or sluggishly reactive organozincs into highly reactive reagents for their reactivity towards various common electrophiles. This includes carbonyl addition reactions of organozinc reagents, which are catalyzed by Pd complexes. 

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