3- Nitrophenylboronic acid

Figure 14 3-Nitrophenylboronic acid and alizarin self-organize in the presence of various anions.

It is clear from Table 32 that A-arylation proceeds very effectively and afforded the corresponding A-arylated products in good to excellent yields under very mild conditions. No spectacular electronic effects were observed in N-arylatimi of aniline only a slight decrease in the reactirai rate was noted with the 3-nitrophenylboronic acid. Next we examined the N-arylation of various primary amines such as aliphatic, cyclohexyl and heterocyclic amines with phenylboronic acid using CuFAP catalyst at room temperature, and the results are listed in Table 33. All the reactions proceeded very efficiently at room temperature and yielded the corresponding N-arylated products. It was interesting to note that the formation of the conceivable diarylated product is not observed in our conditions. 

In a simple strategy to biaryl formation, Han et al.89 showed that silicon-directed ipso-substitution and concomitant cleavage from supports could be used for formation of functionalized biphenyls. For this they used a tethered silyl aryl bromide in a Suzuki cross-coupling reaction, followed by the ipso-substitution/cleavage step (Scheme 39). A variety of boronic acids were coupled in this manner. The only difficulty occurred with electron-deficient nitrophenylboronic acid where the desired product was formed under anhydrous conditions in only 33% yield (the remainder being starting material). Reversion to the more usual conditions of aqueous base-DME (i.e., those used by Frenette and Friesen)70 improved the yield to 82%. 

Nitrophenylboronic acid 25 and 2-bromothiophene 26 were successfully cross-coupled in 15 min under microwave irradiation in a good yield into 2-(2-nitrophenyl)thiophene 27, which by reductive cyclization gave, in good yield, AH- thieno 3,2-/ indole 28 (Scheme 3). 

The reagent L-TarB-N02 (78), prepared from tartaric and /w-nitrophenylboronic acids, asymmetrically reduces ketones in the presence of sodium borohydride.301 Evidence for a monoacyloxyborohydride intermediate (79) is presented. 

The rare, fluorescent indazolo[3,2-Suzuki reaction with o-nitrophenylboronic acid provides the 1-aryliso-quinohnes.This is followed by a microwave-enhanced Cadc an cychzation in... 

Alizarin red S has also been used by Basu with a number of commercial monoboronic acids, it was found that 3-methoxycarbonyl-5-nitrophenylboronic... 

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