Phenylboronic add

Grignard reaction, other examples n-Butyl borate (see Phenylboronic add). r-Butylhydro-peroxide. /-Butylperbenzoate. Dibromodifluoromethane. Diethyl sulfate. Ester synthesis (see 3-Dimethylaminopropylamine). Ethoxymethyleneaniline. Ethyl chloroformate. Ethylene dibromide (entrainment). Ethylene oxide. Ethyl formate. Ethynylmagnesium bromide. Sulfur. Triethyl orthoformate. Trimethylene oxide. See also Dichloroformoxime. 

PROTECTIVE GROUP FOR NUCLEOSIDES 0-Benzoylpropionic add. Tetramethyl orthocarbonate. Phenylboronic add. 

The mode of intramolecular cychzation (5- vs 6-membered ring formation, O vs N attack) of a phenylboronic add equipped with an ortho-hydroxamic add group was determined to be a dehydration leading to the benzo[d][l,2,6]oxazaborinin-4(3H)-one 147 (Scheme 51) (2013AX(C)183). By X-ray, the boron heterocycle 147 is planar and displays both a phenollike OH group and a lactam group. Strong intermolecular O—H-"0=C and N—H- 0=C interactions were noted in its crystal stmcture. 

A very successful way to improve regiospecificity and to minimize branching was the synthesis through transition-metal-catalyzed reactions of monomeric 2,7-dihalogenated fiuorenes. The palladium-catalyzed synthesis of mixed biphenyles from phenylboronic add and aryl bromide discovered by Suzuki et al. [64] tolerates a large variety of functional groups and the presence of water. This method can also be used to prepare perfectly alternating copolymers. 

Under favorable conditions, the hydroxyl group of boronic acids can serve as a nucleophile. For example, epoxy-sulfides are opened stereoselectively by phenylboronic add to afford diol products (Equation 88, Figure 1.41) [465]. A new variant of this process makes use of a palladium catalyst [466]. Boronic acids have been employed recently as internal nudeophiles in a bromo-boronolactonization of olefins (Equation 89) [467]. 

Krische and co-workers reported an intramolecular version of the tandem conjugate addition-aldol reaction. Enone-ketone 59 reacts with phenylboronic add (2m) in dioxane containing 5 equiv. of water [40] (Scheme 4.26). This cyclization probably proceeds through the (oxa-7t-allyl)rhodium intermediate. Because the intramolecular addition of the intermediate to the ketone is faster than protonolysis with water, the al-dol product is obtained in high yields. Binap is a ligand of choice, leading to the conjugate addition-aldol product in up to 95% ee. 

Boronic acids have been used in the development of surface plasmon resonance (SPR) [174,175] quartz crystal microbalance (QCM) sensors [174,176,177], Faradaic impedance spectroscopy [177], ion-sensitive field effect transistors (ISFET) [178], and chemical exchange saturation transfer (CEST) contrast agents in magnetic resonance imaging (MRl) [179]. The swelling of phenylboronic add polymers has also been used to control the release of insulin (180,181]. 

---