Boroxines, Boronic Esters and Trifluoroborate Salts

Batey and Quach have investigated alkenyl and aryl trifluoroborate salts as coupling agents. Their earlier publication [47], disclosed a C-O cross-coupling protocol 

Of the reported procedures for basic alkylamine substrates, the Batey procedure (using arylboronic acids) gave the best yields and is the method of choice. 

In this section we will attempt to pull together the different aspects of the N/O-aryla-tion reaction in order to shed light on the mechanism of the cross oupling reaction. 

this reaction probably does not involve free radicals, as the addition of 1,1-diphenylethylene, a free radical trap, has no effect on the yield of N-arylation of benzimidazole to give p-tolylbenzimidazole. Besides, the presence of triplet oxygen will normally intercept the free radicals. 

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