Secondary alkylzinc derivatives

Remarkably, the methyl group is not transferred in these cross-coupling reactions. Interestingly, the reaction can be extended to secondary alkylzinc derivatives (Scheme 9-29) [58]. 

The reaction of primary and secondary alkylzinc and alkylmagnesium derivatives with alkenyl halides, such as ( )-l-iodo-2-methy-l-hexene, in the presence of 5mol% of PdCPPhj) can proceed to give the desired cross-coupling products in good yields along with only minor amounts (<15%) of the deiodination products [66,67] (Table 1-2). A closer look at the reaction of ec-BuMgCl with ( )-PhCH=CHBr catalyzed by various Pd-phosphine... 

All of the alkyl electrophiles shown in Schemes 73-78 are primary alkyl derivatives. On the other hand, cross-coupling of primary alkylzincs with secondary alkyl iodides and bromides was shown to be feasible with 4% Ni(COD)2, 8% s-Bu-Pybox (3) and DMA(N,N-Dimethylacetamide)88k (Scheme 79). More recently, a modification of this procedure through the use of -Pr-Pybox and 7 1 DMI/THF, where DMI is 1,3-dimethyl-2-imidazolidinone, in place of v-Bu-Pybox (3) and DMA has been shown to permit enantioselective alkylation of racemic secondary a-bromoamides with organozincs210 (Scheme 79). 

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