Pinacol ester of diboronic

A solution of the pinacol ester of diboronic acid (1 mmol), l-bromo-3,4-methylenedioxy benzene (2 mmol), 10% Pd/C (80mg) and CS2CO3 (3.7 mmol) were dissolved in 10ml methyl alcohol and heated to 55 °C 16 hours. GC analysis indicated that the product constituted of 83.5% 2-(bisl,3-benzodioxole and 16.5% l-bromo-3,4-methylenedioxy)benzene. 

The Pd-catalyzed cross-coupling reaction of the pinacol ester of diboronic acid with aryl halides and triflates gives a direct procedure for various functionalized arylboronic esters (Table 6), which are useful for highly efficient and selective carbon-carbon bond formation by Pd catalysts (Sect. III.2.2). The combination of PdCl2(dppf) with KOAc (and dppf) is effective in the carbon-boron bond formation. KOAc is essential not only to accelerate the reaction but also to prevent the formation of biaryl by-products. 

Table 10. Iridium-catalysed borylation of arenes with pinacol ester of diboron (350)...

A mixture of pinacol ester of diboron (350,280 mg, 1.1 mmol), potassium acetate (300 mg, 3 mmol) and Pd(dppf)Cl2 (3 mol%) was flushed with nitrogen. DMSO (6 ml) and 4-bromoacetophenone (73, 200 mg, 1 mmol) were then added. After being stirred at 80 C for 1 h under nitrogen, the product was extracted with toluene, washed with water and dried over Na2S04. Kugelrohr distillation in vacuo gave 197 mg (80%) of pure 4-acetylphenyl-pinacolboronate (368). 

The Pd-catalyzed cross-coupling reaction of the pinacol ester of diboronic acid with aryl halides and triflates gives a direct procedure for various functionalized arylboronic esters (Table which are useful for highly efficient and selective carbon-carbon bond... 

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