Organozinc compounds cross-coupling

Scheme 5.2-20 Pd-catalyzed cross-coupling of organozinc compounds (Negishi cross-coupling)...

The first examples of microwave-assisted cross-couplings with organozinc compounds were recently reported [47]. In addition, the first high-speed synthesis of aryl boronates (Suzuki coupling reactants) has been performed under the action of single-mode irradiation with an in-situ-generated palladium carbene catalyst [48],... 

The cross-coupling reaction of thiomethylpyrimidines 99 with organozinc compounds 100 in the presence of palladium was found to produce pyrimidines 101 in good to excellent yields <00SL905>. 

Recent notable improvements by Knochel and co-workers include iron-catalyzed cross-coupling reactions of various acid chlorides 148 with dialkylzinc reagents (Equation (24))324 as well as the iron-catalyzed arylation of aroyl cyanides 149 with Grignard reagents (Equation (25)).3 5 In the first case Knochel s reaction conditions tolerate ester groups on the organozinc compounds, while in the latter case ester, aryl alkyl ether, cyano, and chloro functionalities on the aromatic moieties are compatibles with the reaction conditions. 

Grigg employed organozinc chemistry to construct 3-alkylidenedihydroindoles such as 91 via a tandem Pd-catalyzed cyclization-cross coupling sequence [112]. A similar route to such compounds was reported by Luo and Wang e.g., 92 to 93 [113]. 

In addition, the organozinc compound obtained from ethyl 4-bromobutanoate reacts under similar conditions to those described previously, with 4-bromoacetophenone, to give the corresponding product in good yield15. The preparation of organozinc compounds and their cross-coupling with aryl halides can be carried out in one step (equation 7). 

For transition metal-catalyzed cross-coupling of organozinc compounds, see the appropriate transition metal (Ni page 382, Section 20 Pd page 386, Section 21 Cu page 392, Section 22). 

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