Emergent Organoboron Acid Catalysts

Abstract

Organoboron acids are stable, organic-soluble Lewis acids with potential application as catalysts for a wide variety of chemical reactions. In this review, we summarize the utility of boronic and borinic acids, as well as boric acid, as catalysts for organic transformations. Typically, the catalytic processes exploit the Lewis acidity of trivalent boron, enabling the reversible formation of a covalent bond with oxygen. Our focus is on recent developments in the catalysis of dehydration, carbonyl condensation, acylation, alkylation, and cycloaddition reactions. We conclude that organoboron acids have a highly favorable prospectus as the source of new catalysts.

Figure 1.

Structures of the various oxidation states of organoboron derivatives. R¹, R², R³ = alkyl, aryl, vinyl, alkynyl.

Figure 2.

Representative reactions that are catalyzed by organoboron acids: dehydration, carbonyl condensation, acylation, alkylation, and cycloaddition. R¹, R² = alkyl, aryl, vinyl, alkynyl, hydroxy.

Figure 3.

Key intermediates proposed by (A) Ishihara, (B) Ishihara, and (C) Whiting in the activation of carboxylic acids toward nucleophilic attack through complexation with arylboronic acids to form an acyloxy boronic acid.

Figure 4.

Activation of oxygen atoms as nucleophiles by complexation with a borinic acid. Complexation of a diol with a boronic acid leads to a neutral complex and no additional electron density on the oxygen atoms. The anionic complex formed with a borinic acid leads to an increase in electron density on oxygen and its activation as a nucleophile.

Figure 5.

Strategy for the in-situ formation of a chiral Brønsted acid from 2-carboxyphenylboronic acid and a chiral diol. Internal coordination of the carboxylic acid to the boronic acid increases the Brønsted acidity.

Figure 6.

Change in C–H bond energies in rhamnopyranosides upon formation of a complex with diphenylborinic acid. Data were calculated in the gas phase with the B97-D3/Def2-TZVP level of theory.

Scheme 1.

Boronic Acid Catalyzed Dehydration of Biomass-Derived Glucose to 5-Hydroxymethylfurfural

Scheme 2.

Catalysis of Anhydride Formation by an o-Dialkylaminomethyl-Substituted Phenylboronic Acid.^–

Scheme 3.

Boric Acid Catalyzed Formation of Benzimidazoles from Diamines and Carboxylic Acids

Scheme 4.

Boric Acid Catalyzed Synthesis of a 1,2,4-Triazolopyridinone

Scheme 5.

Stereoselective Catalysis of the Dehydration of an anti Aldol Reaction Product by a Borinic Acid

Scheme 6.

Boronic Acid-Accelerated Formation of Oximes for Bioconjugation

Scheme 7.

Hydrolysis of a Salicylaldehyde Imine, Catalyzed by Boric Acid or a Boronic Acid through the Stabilization of a Hemiaminal Intermediate

Scheme 8.

Catalysis of an Aldol Reaction by a Benzimidazole-Substituted Phenylboronic Acid

Scheme 9.

Aldol Addition Through Combined Enamine–Boronic Acid Catalysis by Homoboroproline

Scheme 10.

Catalysis of Isotetronic Acid Synthesis by a Borinic Acid

Scheme 11.

Boric Acid Catalyzed Biginelli Reaction for the Production of 3,4-Dihydropyirimidin-2(1H)-ones

Scheme 12.

Catalysis of a Three-Component Ugi Reaction by Boric Acid in Water

Scheme 13.

Boric Acid Catalyzed Synthesis of a Thiopyridine via a Three-Component Condensation

Scheme 14.

Solvent-Free Four-Component Condensation Catalyzed by Boric Acid and Water

Scheme 15.

Catalysis of a Three-Component Synthesis of a Tetrahydrobenzo[b]pyran by Phenylboronic Acid

Scheme 16.

Catalysis of a Three-Component Condensation by Pentafluorophenylboronic Acid

Scheme 17.

Arylboronic Acid Catalysts Reported by Yamamoto and Wang for the Formation of Amide Bonds

Scheme 18.

Boric Acid Catalyzed Selective Esterification of an α-Hydroxycarboxylic Acid

Scheme 19.

Catalytic Amidation of a β-Hydroxycarboxylic Acid using a Diboronic Acid Anhydride

Scheme 20.

Borate Ester-Catalyzed Amidation.

Scheme 21.

Boronic Acid Catalyzed Amidation

Scheme 22.

Borinic Acid Catalyzed Site-Selective Monoacylation of a Carbohydrate

Scheme 23.

Boronic Acid Catalyzed Site-Selective Monoacylation of a Carbohydrate

Scheme 24.

Borinic Acid Catalyzed Formylating Transamidation with DMF

Scheme 25.

Boronic Acid Catalyzed Beckmann Rearrangement

Scheme 26.

Boronic Acid Catalyzed Friedel–Crafts Alkylation

Scheme 27.

Synthesis of Asymmetric Diarylmethanes, Catalyzed by Ferroceniumboronic Acid

Scheme 28.

Indole Addition to Nitroolefins Through Boron-Assisted Brønsted Acidity

Scheme 29.

Boronic Acid Catalyzed Dehydrative Etherification.

Scheme 30.

Boron-Templated Acid Catalyzed Dimerization of Allylic Alcohols

Scheme 31.

Boronic Acid Catalyzed Allylation of an Oxime

Scheme 32.

Ether Exchange of Methoxynitroarenes Promoted by Phenylboronic Acid Pinacol Ester

Scheme 33.

Ene Carbocyclization of Pendant Alkynes, Catalyzed by a Boronic Acid

Scheme 34.

Boronic Acid Catalyzed Site-Selective Epoxide Aminolysis

Scheme 35.

Catalysis of Nitrocyclopropane Ring-Opening by a Urea-Substituted Arylboronic Acid

Scheme 36.

Boronic Acid-Catalyzed Desymmetrization of a 2-Aryl-1,3-propanediol

Scheme 37.

Catalysis of O-Glycosylation by an Imidazole-Substituted Phenylboronic Acid

Scheme 38.

Catalysis of O-Glycosylation by an p-Nitrophenylboronic Acid

Scheme 39.

Catalysis of C-Glycosidation by Boric Acid and Pyrrolidine

Scheme 40.

Phase-Transfer Catalysis of O-Glycosidation by Phenylboronic Acid

Scheme 41.

Boric Acid-Catalyzed aza-Michael Addition

Scheme 42.

Catalysis of an Enantioselective aza-Michael Addition by a BINOL Boronic Acid

Scheme 43.

Catalysis of an Asymmetric aza-Michael Addition by a Thiourea-Substituted Phenylboronic Acid

Scheme 44.

Boronic Acid-Catalyzed Reductive Alkylation of a Quinoline

Scheme 45.

Enantioselective 1,4-Addition Reaction, Catalyzed by a Boronic Acid and Chiral Amine.

Scheme 46.

Borinic Acid-Catalyzed Regioselective N-Alkylation of an Azole Heterocycle

Scheme 47.

Boronic Acid-Catalyzed [4 + 2] Cycloaddition

Scheme 48.

Boronic Acid-Catalyzed [3 + 2] Cycloaddition

Scheme 49.

Boronic Acid-Catalyzed [4 + 3] Cycloaddition

Scheme 50.

Borinic Acid-Catalyzed Epoxide Ring-Opening with (A) a Halide, (B) a Sulfonyl or Acyl Chloride,^, and (C) a Semipinacol Rearrangement

Scheme 51.

Boronic Acid-Catalyzed Asymmetric Aziridination of an Imine

Scheme 52.

Boronic Acid Catalyzed Oxidation of a 1,2-Diol to an α-Hydroxy Ketone

Scheme 53.

Borinic Acid Catalyzed Oppenauer Oxidation of an Alcohol

Scheme 54.

Boronic Acid Catalyzed Site-Selective Photochemical Oxidation of an Unprotected Carbohydrate

Scheme 55.

Boronic Acid Catalyzed Reduction of an Amide with a Silane

Scheme 56.

Boronic Acid Promoted Selective Reduction of Aldehydes

Scheme 57.

Borinic Acid Catalyzed Reduction of Phosphine Oxides, Sulfoxides, and Amine N-Oxides

Scheme 58.

Catalysis of the Reductive Formylation of an Amine with Carbon Dioxide by a Sodium Phenylboronate Salt

Scheme 59.

Boronic Acid Catalyzed Synthesis of a Cyclic Carbonate from an Epoxide and CO₂

Scheme 60.

Boronic Acid Catalyzed Site-Selective Silylation of a Pyranoside

Scheme 61.

Boric Acid Catalyzed Trimethylsilylation and Deprotection of an Alcohol

Scheme 62.

Hydrostannylation of an Alkyne, Promoted by Boric Acid

Scheme 63.

Photocatalytic Alkylation of a Carbohydrate, Directed by a Borinic Acid

Scheme 64.

Photocatalytic Oxidation of a Furanoside, Directed by a Boronic Acid