Organoboron Acids and Their Derivatives as Catalysts for Organic Synthesis

Abstract

An overview of the applications of boronic and borinic acids in catalysis is presented. Taking advantage of the Lewis acidity of trivalent boron and the reversible covalent interactions of organoboron acids with OH groups, diverse modes of catalytic reactivity have been achieved. Interactions with carbonyl compounds enable acceleration of addition and cycloaddition processes, whereas binding of their enol tautomers can lead to organoboron-catalyzed aldol and related reactions. Binding of organoboron acids to hydroxyl and carboxyl OH groups has been employed as a mode of electrophilic activation for catalysis of substitution, cycloaddition, rearrangement, and elimination reactions. By altering the nature of the interaction with the organoboron acid catalyst, activation of OH groups as pronucleophiles is also possible, resulting in catalyst-controlled methods for regioselective functionalization of diols and carbohydrate derivatives. Applications of organoboron acids in bifunctional and assisted catalysis are also discussed.

Scalable, Metal- and Additive-Free, Photoinduced Borylation of Haloarenes and Quaternary Arylammonium Salts

“…Aromatic boronic acids find increasingly important roles in the areas of synthetic organic chemistry, 1 catalysis, 2 molecular self-assembly, 3 carbohydrate analysis, 4 molecular sensing, 5 materials science 6 and medicinal chemistry. 7 While the reaction of organomagnesium and organolithium reagents with trialkyl borates, first described by Khotinsky (RMgX) 8 and Letsinger (RLi), 9 remains in use, transition metal-catalyzed C–X- 10 and C–H-borylation 11 reactions have recently emerged as efficient alternatives that bypass air- and moisture-sensitive intermediates.…”

Theoretical Investigations toward the Asymmetric Insertion Reaction of Diazoester with Aldehyde Catalyzed by N-Protonated Chiral Oxazaborolidine: Mechanisms and Stereoselectivity

“…It should be noted that the prefix "H_" represents the formal C−H insertion reaction of aldehyde via [1,2]-hydrogen migration, while the prefix "Ph_" represents the formal C−C insertion reaction of diazoester into aryl-CHO via [1,2]-migration of phenyl group. We also marked the chirality of the C3 atom in bold R/S and the chirality of C6 atom in bold and italic R/S for the sake of clarity.…”

“…34, 13.53, 18.76, and 15.35 kcal/mol, respectively. It is noteworthy that the lowest energy barrier for the migration of hydrogen (via TS2(SS), 15.35 kcal/mol) is a little higher than that for the migration of the phenyl group (via TS2(RS), 13.53 kcal/mol), so the α-benzyl-β-ketoester H_P(R/S) can still be obtained via the [1,2]-hydrogen migration. The energy barrier of the favorable C−C insertion reaction pathway is 1.82 kcal/ mol lower than that of the favorable C−H insertion reaction pathway, indicating that the C−C insertion reaction should be more energy favorable and Ph_P(R) should be the main product; this is in agreement with the experimental observations.…”

“…Moreover, there are still some questions which need to be answered for the novel organocatalytic reaction: (1) How does this kind of reaction happen in detail? (2) Which is the stereoselectivity determining step? (3) What are the factors that control the stereoselectivities of the title reaction?…”

Recent Advances in Organocatalytic Glycosylations

“…Trivalent boron possesses catalytically useful Lewis acidic electronics and exhibits a propensity to reversibly form boron–carbon and boron–oxygen bonds. Furthermore, there is extensive literature on the molecular recognition of carbohydrates by organoboron derivatives through binding to cis ‐1,2 diol groups in a tetracoordinate manner . Harnessing these properties in a synthetically useful context makes organoboron catalysis a valuable addition to the organocatalytic glycosylation toolbox …”