2-Methoxyphenylboronic acid

Martin effected the synthesis of several 3,5-diarylated indoles by a tandem Stille-Suzuki sequence [131]. The latter reaction involves exposure of 3-(3-pyridyl)-5-bromo-l-(4-toluenesulfonyl)indole with arylboronic acids (aryl = 3-thienyl, 2-furyl, phenyl) under typical conditions to give the expected products in 86-98% yield [131], Carrera engaged 6- and 7-bromoindole in Pd-catalyzed couplings with 4-fluoro- and 4-methoxyphenylboronic acids to prepare 6- and 7-(4-fluorophenyl)indole (90% and 74% yield) and 6-(4-methoxyphenyl)indole (73% yield) [29]. Banwell and co-workers employed 7-bromoindole in a Suzuki coupling with 3,4-dioxygenated phenylboronic acids en route to the synthesis of Amaryllidaceae alkaloids [132], Yields of 7-arylated indoles are 93-99%. Moody successfully coupled 4-bromoindole... 

Snieckus et al. enlisted a combination of directed orrAo-lithiation and Suzuki coupling to assemble some unsymmetrical heterobiaryls [22], Carboxamidophenylboronic acid 30 was derived from sequential metalation of amide 29 and treatment with B(OMe)3 followed by acidic workup. Hetero cross-coupling of 30 with 2-bromothiazole occurred smoothly to furnish phenylthiazole 31. Similarly, a hetero cross-coupling between 2-bromothiazole and 3-formyl-4-methoxyphenylboronic acid produced a heterobiaryl as an intermediate of an orally bioavailable NKi receptor antagonist [23]. 

B. 2-(4-Methoxyphenyl)-2-cyclohexen-1-one. A 500-mL, round-bottomed flask, equipped with a 1.5-in. Teflon-coated magnetic stirring bar and an argon inlet adaptor, is charged with 10.02 g (45.1 mmol) of 2-iodo-2-cyclohexen-1-one, 10.69 g (70.4 mmol, 1.56 eq) of 4-methoxyphenylboronic acid (Note 8), 16.72 g (72.1 mmol, 1.6 eq) of silver(l) oxide (Ag20) (Note 9), 0.85 g (2.8 mmol, 6 mol %) of triphenylarsine (Note 10), 0.53 g (1.4 mmol, 3 mol %) of palladium(ll) bis(benzonitrile)dichloride (Note 11), 200 mL of tetrahydrofuran (THF) and 25 mL of water (Note 12). The reaction mixture, flushed with argon, is stirred for 1 hr and then quenched by the addition of 125 mL of saturated aqueous ammonium chloride. After the solution is stirred for 1 hr, the... 

Methoxyphenylboronic acid can be purchased from Aldrich Chemical Company, Inc. 

METHOXYPHENYL)-2-CYCLOHEXEN-1-ONE PREPARATION OF 2-IODO-2-CYCLOHEXEN-1-ONE AND SUZUKI COUPLING WITH 4-METHOXYPHENYLBORONIC ACID (2-Cyclohexen-1-one, 2-(4-methoxyphenyl)- and 2-Cyclohexen-1-one, 2-iodo-)... 

We have subsequently revisited this reaction and successfully optimized the Suzuki microwave-assisted coupling conditions using the Smith synthesizer. Several parameters were investigated, including the palladium catalysts, the reaction temperatures, and the reaction times (Table I). Optimization reactions were run in the Smith synthesizer using 50 mg of resin 7 and 6 equivalents of 4-methoxyphenylboronic acid to afford oxa-zolidinone 8. In just a few days, optimized conditions were identified that afforded the desired product in excellent yields and purities with reactions times of only 5-10 min.8... 

Suzuki coupling reactions of 16 with 4-methoxyphenylboronic acid and 2-ben zo[ h] thiophene-2-boronic acid in the presence of Pd(PPh3)4 and aqueous NaHC03 as base, in a mixture of toluene/ethanol (5 1) at 90 °C for 2 h, afforded the corresponding coupling products in high yields (Eq. (45)) [76]. 

In the course of a study of structure-based design and synthesis of a potent matrix metallo-proteinase-13 inhibitor based on a pyrrolidinone scaffold, the Suzuki coupling reaction of a,/ -unsaturated /-lactam iodide (40) with 4-methoxyphenylboronic acid was carried out to give the corresponding coupling product in 77 % yield (Eq. (76)) [119]. 

N-Arylation of ethyl l/f-pyrrole-2-carboxylate under Chan and Lam conditions <1998TL2933, 1998TL2941>, by reaction with 4-methoxyphenylboronic acid in the presence of cupric acetate and either triethylamine or pyridine at room temperature, gave the pyrrole ester 190 in good yield (Equation 40) <1999T12757>. 

Cytoxazone is a novel cytokine modulator. The total synthesis of this natural product and its enantiomer was accomplished by S. Sugiyama. The 3-amino-1,2-propanediol moiety was synthesized by a Petasis boronic acid-Mannich reaction between DL-glyceraldehyde, (R)-1-(1-naphthyl)ethylamine and 4-methoxyphenylboronic acid to provide a 1 1 mixture of the diastereomeric products. The diastereomers could be separated at a later stage in the synthesis and transformed into (-)- and (+)-cytoxazone. 

A key intermediate required for the synthesis of colenterazine was reported by Adamczyk et al. [46]. Treatment of 3-benzyl-5-bromo-2-pyrazinamine (77) with commercially available 4-methoxyphenylboronic acid in the presence of dppb and Pd(PhCN)2Cl2 afforded 3-benzyl-5-(4-methoxyphenyl)-2-pyrazinamine (78) in 88% yield [46]. 

The MP group is introduced on a sulfonamide through a Cu(OAc)2 catalyzed coupling with 4-methoxyphenylboronic acid. It can in principle be cleaved oxidatively with DDQ. 

Figure 2.29 shows the synthesis of 44 from acenaphthene.94 Suzuki-Miyaura coupling of 3-bromoacenaphthene (A) with 4-methoxyphenylboronic acid (B) was the key step to give C in 86% yield. 

Axially chiral guanidines with an external guanidine unit such as dinaphthoazepineamidine are effective catalysts for the enantioselective addition of p-oxoesters and a 1,3-diketone to di-ferf-butyl azodicarboxylates to yield cx-hydrazino-p-oxoesters and a-hydrazino-p-dike-tones in 54-99% yields and in 15-98% ee [44]. For example, stirring 2-oxocyclopenta-necarboxylate and di(tert-butyl) azodicarboxylate in THF in the presence of 0.05 mol% catalyst for four hours at —60° C provides an adduct in quantitative yield and in 97% ee (Scheme 4.15). The (R)-catalyst was prepared from (/ )-2,2 -dimethyl-3,3 -binaphthalene-diol ditriflate, 4-methoxyphenylboronic acid and 3.5-di(rert-butyl)phenylboronic acid in six steps. 

Exploiting the bromo functionality on some of the generated U-shaped azaacenes, they were functionalized further via palladium-catalyzed processes either with 4-methoxyphenylboronic acid, morpholine, piperidine,... 

Meyer-Schuster rearrangements of secondary and tertiary propargylic alcohols occur readily with PPh3AuNTf2, in the presence of 4-methoxyphenylboronic acid or 1 equiv. of methanol to give enones with high selectivity for the -alkene (Scheme 117). ... 

BocHN)-4-methoxyphenylboronic acid (Eq. 5) A solution of f-BuLi in pentane (1.7 M, 340 mmol) is added to a solution of t-butyl 4-methoxy-carbanilate (136 mmol) in ether (500 mL) at -20 °C. After stirring for 5 h at -20 °C, (MeO)3B (408 mmol) is added. The resulting viscous solution is swirled manually for 5 min, then allowed to warm to 23 °C and to stand for 12 h. The solution is partitioned between saturated aqueous NH4CI (500 mL) and ethyl acetate (500 mL). The aqueous layer is extracted further with ethyl acetate (2 x 500 mL) and the combined organic layers are dried over MgSO. The product is purified by flash chromatography (2.5% MeOH in CHjClj -> 10% MeOH in CHjClj) to provide boronic acid (19.9 g, 55%). 0.43 (10% MeOH in CHjClj). 

Pd(0), DIEA, 100°C, 3 days, 4-methoxyphenylboronic acid or PdCl2(dppe), Cul, DIEA, 3-methylpentyn-3-ol, 80 C 36 h... 

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