Discuss one method of synthesis of organozinc compounds
Answers
Answer:
Organozinc compounds are more reactive nucleophiles requiring no activation for the transmetalation step, while allowing for much wider functionality to be present in the molecule than in organomagnesium compounds. However, organozinc compounds cannot be stored without special precautions, and therefore should be generated immediately prior to use, which makes them much less convenient than organoboron and organotin compounds. Thus, the cross-coupling with organozinc compounds (commonly referred to as the Negishi reaction) is a more specialized method; it is, however, indispensable when the combination of high reactivity and maximal tolerance to functionality in the coupling partners is required.
Sources for the organozinc compounds are as follows:
(i)
Organozinc compounds, including aryl or heteroaryldizinc reagents, can be prepared by electrosynthesis using a sacrificial Zn anode.
(ii)
Halogen–zinc metathesis can be accomplished by the reaction of organic halides with simple dialkylzinc reagents.
(iii)
Zirconocene dichloride and similar complexes catalyze carbozincation of alkenes and alkynes.101,102 Carbozincation of alkynes103,104 can also be performed with nickel catalysis. The methods of generation of functionalized organozinc reagents have been reviewed.
353573653547564686886