Butylboronic acid

The oxidation of rm-butylboronic acid by chromic acid has the stoichiometry... 

The tartaric acid scaffold also led to the design of one of the most effective and general methods to generate enantiomerically enriched substituted cyclopropyhnethanol derivatives. Indeed, the chiral dioxaborolane ligand 19, prepared from tetramethyltartramide and butylboronic acid, is a superb chiral additive in allylic alcohol-directed cyclopropanation reactions (equation 83) . The best procedure requires the use of the soluble bis(iodomethyl)zinc DME complex . The reaction affords high yields and enantiomeric... 

Gas chromatographic separation of -agonist residues is generally complicated by the necessity of derivatization of their polar hydroxyl and amino functional groups. Silyl derivatives are preferentially prepared by treating sample extracts with N,0-bis(trimethylsilyl)trifluoroacetamide (470,471,473,475,483, 487), N-metliyl-N-(trimethylsilyl)trifluoroacetamide (482) or N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (473, 487). Pentafluoropropionic anhydride (481), phosgene (484), trimethylboroxine (480), methyl- and butylboronic acid (489), or a combination of N,O bis(trimethylsilyl)trifluoroacetamide with... 

SPE cleanup, derivatization with methyl- and butylboronic acid... 

Bromo-l-[bis(trimethylsilyl)amino]butylboronic acid pinanediol ester (26) was prepared by first dissolving hexamethyldisilazane (16.9 mL, 80.0 mmol), in THF (30 mL), cooling the soln to —78 °C, and adding 1.62 M BuLi in hexane (49.4 mL, 80.0 mmol). The soln was allowed to slowly warm to rt. It was recooled to —78°C and 4-bromo-l-chlorobutylboronic acid pinanediol ester (25 28.0 g, 80.0 mmol), was added in THF (20 mL). The mixture was allowed to slowly warm to rt and to stir overnight. The solvent was removed by concentration and dry hexane (400 mL) was added to yield a precipitate, which was removed by filtration under N2. The filtrate was cooled to —78 °C and 4 M anhyd HC1 in dioxane (60 mL, 240 mmol) was added. The reaction was allowed to slowly warm to rt and stirred for 2h. Additional hexane can be added to aid in precipitation. The product was isolated as a solid (20 g) by filtration. After drying in vacuo, the crude product was dissolved in CHC13 and insoluble material was removed by filtration. The filtrate was concentrated and the residue dissolved in EtOAc. The product 27 was crystallized (EtOAc) yield 15.1 g (51%) mp 142-144°C. 

Ware and Traylor17 have shown that the reaction of chromic acid with tert.-butylboronic acid, viz. 

Preparative Methods the reagent is easily prepared from commercially available butylboronic acid (or its more stable diethanolamine complex) and RJi)-(+)-N,NJ4 J4 -tetramethyltartaric acid diamide. The other enantiomer is also... 

Problems with the preparation and stability of oxazaborolidine (6) led to the development of a series of B-substituted ox-azaborolidines derived from diphenylprolinol. The B-methyl substituted oxazaborolidine (9a) was first prepared (eq 5) by reaction of diphenylprolinol (1) with methylboronic acid under dehydrating conditions (toluene at 23 °C in the presence of 4 X molecular sieves or toluene at reflux using a Dean-Stark trap) followed by vacuum distillation (0.1 mmHg, 170°C). Based on NMR evidence, the product (mp 74-87 °C) was reported to be a mixture of monomer and dimer. The corresponding B-butyloxazaborolidine (9c), prepared in a similar manner from n-butylboronic acid, was also reported to be a mixture of monomer and dimer. Subsequent investigations demonstrated that the reported dimers were in fact the intermediate (8) and the more stable disproportionation product (10) (eq 6). Furthermore, the presence of (8) or (10) was demonstrated to be deleterious to the enantioselectivity of the catalyst. ... 

With the /i-butylboronic acid, a semiclathrochelate intermediate product was not pre-isolated and the clathrochelate complex was produced from a template reaction [185]. 

Figure 28. kobs as a function of H+ ion concentration in the absence of n-butylboronic acid for the FeNx3(Bn-C4H9)2 complex [288],... 

However, this asymmetric cyclopropanation of allylic alcohols can be used only up to 1 mmol equivalent. When run on a larger scale, e.g. 8 mmol, a violent explosion of the reaction mixture was observed. Accordingly, the authors have improved the procedure by adding the bis(iod-omethyl)zinc reagent as its 1,2-dimethoxyethane complex in dichloromethane. The cyclo-propanations were safely carried out on > 1 mmol scale with 93% ee and > 98% yield, e.g. cyclopropanation to give 95. The chiral alcohol and butylboronic acid could be recovered and used again. 

To a solution of (-l-)-A,A,iV, A -tetramethyltartaric acid diamide (30.6 g, 0.15 mol) in anhyd toluene (100 mL) was added butylboronic acid (18.3 g, 0.18 mol). The mixture was heated under reflux in a Dean-Stark apparatus for 15 h to remove the water produced in the reaction. The mixture was cooled to rt and concentrated under reduced pressure. The residue was dissolved in a minimum of CH2CI2, filtered to remove the excess of butylboronic acid and concentrated under reduced pressure yield 37.8 g (93%). 

Butylboronic acid 1-Butaneboronic acid (8) Boronic acid, butyl- (9) (4426-47-5) Trimethyl borate Boric acid, trimethyl ester (8,9) (121-43-7)... 

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