Kumada reactions synthetic application

Conveniently prepared from phenols, more readily available than the corresponding aryl halides, and recognized as the most powerful in the hierarchy of DMGs [63], the aryl O-carbamates are primed for synthetic application. One application is their use in the regioselective preparation of polysubstituted aromatics and then involvement as leaving groups in subsequent Suzuki-Miyaura or Kumada-Corriu (Section 14.3.1.2) cross-coupling reactions for the establishment of 1,2-disubstituted aromatics, illustrated by the conceptual 1,2-dipole synthetic equivalent, 35 36 = 37 (Scheme 14.10 and Scheme 14.11) [64]. 

Until recently, little attention has been paid to the synthetic potential of this oxidative cleavage. Due largely to the studies of Tamao and Kumada and, independently, those of Reming, and their coworkers, such potential has now been revealed. It is the purpose of this chapter to highlight some of its applications. Since the emphasis is on synthetic utility, only high-yielding reactions have been selected for inclusion. Unless otherwise stated, 1 compounds shown are racemic only one enantiomer is shown for clarity. 

Although discovered and assessed in scope and limitation over a decade ago [68, 74], the aryl O-carbamate cross-coupling partner for the Kumada-Corriu reaction has not seen widespread application. This conceptual 1,2-dipole synthetic equivalent (Scheme 14.10) has been reasonably well tested using simple, not necessarily always aromatic, Grignard reagents and these have been compared with the... 

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