Intermolecular carbozincations

Transition metal-catalyzed/promoted intermolecular carbozincations... 

Transition metal-catalyzed intermolecular carbozincations of alkenes 881... 

Arylzinc reagents are completely inert towards alkenes and alkynes in the absence of any added catalyst, whereas the reported examples of uncatalyzed intermolecular carbozincations involving alkylzincs appear to be restricted to the more nucleophilic di(tert-butyl)zinc. 

Thus, whereas intermolecular carbozincations of alkenes and alkynes appear restricted in scope and limited to the more reactive di(terf-butyl)zinc, the zinc-induced cyclization of... 

In a useful intermolecular carbozincation process, a vinylzinc reagent reacts with allyl halides to give good to excellent yields of the unconjugated 1,4-diene (equation 105)415. The reaction is highly regioselective and occurs at room temperature in 10-20 minutes. 

Cyclizations of iodoalkynes have also been demonstrated to proceed with C-C bond formation (Scheme 3-89). Little mechanistic information is available for this process, but a net syn addition across the alkyne was noted. Additionally, intermolecular carbozincations of alkynes were demonstrated under similar... 

Scheme 10.37 Copper-catalyzed directed intermolecular carbozincation of cyclopropenecar-boxylates scope of the method [34].

Similarly, zincated hydrazone derivatives of type 56 undergo an intermolecular carbozincation of strained cyclopropene rings such as 57 leading to the adduct 58 with 92% yield [63]. This type of addition can be extended to ethylene ]63c]. It proceeds with an excellent stereoselectivity allowing the enantioselective synthesis of a-substituted ketones. Allylic zinc species also add to cyclopropenone acetals... 

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