Arylboron Compounds Research Articles

Recent Developments of Arylboron Compounds as Lewis Acid Catalysts

Arylboron compounds with electron-withdrawing substituents at their aryl groups are water tolerant Lewis acid catalysts for various carbon-carbon bond formation reactions. For examples, tris (pentafluorophenyl)boron catalyzes aldol-type reaction of aldehydes and imines with silyl enol ethers, stereoselective rearrangement of epoxides, hydrosilation of carbonyl compounds, etc. 3, 4, 5-Trifluorophenylboronic acid promotes amidation reaction between carboxylic acids and amines. Bis (pentafluorophenyl) borinic acid catalyzes substrate selective dehydration reaction of anti-aldols, and Oppenauer oxidation of allylic, and benzylic alcohols.

Protodeboronation of arylboronic acids and triarylboroxines in Bu 20/THF

The arylboron compounds Ph 3B 3N 3Me 3, Ar 3B 3O 3, or ArB(OH) 2 (Ar  Ph, p-BrC 6H 4, p-MeC 6H 4, m-NH 2C 6H 4 react with [Cr(CO) 6] in refluxing Bu 2O/THF (9:1) to afford the (η 6-arene) tricarbonyl-chromium(O) complexes of the protodeboronated substrates in yields of up to 55%. The proposed mechanism involves protodeboronation of the arylboron compound followed by complexation of the free arene by the chromium carbonyl moiety.

ChemInform Abstract: Palladium‐Catalyzed Cross‐Coupling Reactions of Aryl and Vinylic Boron Compounds with Organic Halides

A general and convenient method for the stereo-and regioselective synthesis of conjugated alkadienes, alkenynes, arylated alkenes, and heterobiaryls is described. The reaction of (E) -or (Z) -1-alkenylboronates obtainable by hydroboration, with either (E) -or (Z) -1-alkenyl halides in the presence of a catalytic amount of tetrakis (triphenylphosphine) palladium and bases such as sodium alkoxides gives the corresponding (E, E) -, (E, Z) - (Z, E) -and (Z, Z) -alkadienes stereo-and regioselectively, while retaining the configuration of both the starting alkenylboronates and haloalkenes The similar reactions of (E) -and (Z) -1-alkenylboronates with 1-alkynyl, aryl, allylic, and benzylic halides also provide the corresponding couplig products stereosoelectively. The versatility of this method has been demonstrated by the synthesis of some natural products bearing conjugated alkadiene structures. The reaction of arylboronic acids with aryl halides to give unsymmetrical biaryls is also presented. A mechanism of this cross-coupling reaction, which involves the transmetallation between a 1-alkenylborane and an alkoxopalladium (II) complex generated through the metathetical displacement of a halogen atom of RPd (II) X with sodium alkoxide, is proposed.

Arylboronic compounds—VIII : Some reactions of hydroxy and carboxyphenylboronic acids

Some new derivatives of carboxy and hydroxyphenylboronic acid (I–VI) have been prepared and the direct halogenation of ortho and para hydroxy and methoxyphenylboronic acids has been investigated.

Intramolecular Charge-Transfer Bands Observed in the Spectra of Some Aryl Boron Compounds

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Arylboronic Acids. V. Methyl-substituted Boronic Acids, Borinic Acids and Triarylborons1,2

A number of arylboron compounds bearing o- and pmethyl substituents are prepared and studied. Whereas 2,6-dimethylbenzeneboronic anhydnide is shown by molecular weight determinations to be a trimer, mesityleneboronic anhydride is a dimer, for which a four-membered boron-oxygen ring is proposed. The former yields a complex with pyridine, but only spectral evidence for a pyridine- mesityleneboronic anhydride complex is noted. Under mild conditions, dimesityleneboronic acid is not dehydrated nor is the anhydride hydrated to the acid. Trimesitylboron is nitrated to yield a hexanitro derivative. 2-Mesityl- 1,3-dihydro-2, 1, 3-benzoboradiazole, prepared from mesityleneboronic acid and o- phenylenediamine, is shown to be more resistant to cleavage by hydrochloric acid than is the 2-phenyl homolog. The preparation of 6methylboronophthalide and some proton magnetic resonance studies of arylboron compounds are reported. (auth)