Organo boron halides

Several methods are available for the synthesis of boronic acids and their esters (see also refs. 1-8, 5.3.2.4). Trialkoxyboranes react with polar organometallics. Organo-magnesium halides and organolithiums are most often used. 

The most important palladium-catalyzed processes include Heck vinylation of halides and sulfonates and various cross-coupling reactions in which a nucleophilic intermediate (stannane, organo-zinc halide or boronic acid) is coupled with an electrophile (halide or sulfonate). These coupling reactions are usually restricted to arylation and vinylation because of the tendency of alkylpalladium species to undergo elimination. The pyrrole and indole rings can participate in cross-coupling as either the nucleophilic or electrophilic component. 

De, D. Krogstad, D.J. Pd(DIPHOS)2-catalyzed cross-coupling reactions of organo-borons with free or polymer-bound aryl halides. Org. Lett. 2000, 2, 879-882. 

Due to the sheer volume and variety of Suzuki-Miyaura cross-coupling, it is unrealistic to summarize all the developments in one book chapter. Hence, in this section, we have categorized the cross-coupling reaction based on the nature of organo boron and organo halide. In the subsequent section, we have summarized several applications of these reactions in the total synthesis of natural products. Even in the synthesis section, many of the important applications could not be included due to the space constraints. 

Catalysts. The choice of the proper catalyst lor an esterification reaction is dependent on several factors. The most common catalysis used are strong ininerul acids such as sulfuric and hydrochloric acids. Lewis acids such as boron irifluoride, tin and zinc salts, aluminum halides, and organo-tiianates have been used. Cation-exchange resins and zeolites are often employed also... 

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