Emergent Organoboron Acid Catalysts

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.

Development of fluorous boronic acid catalysts integrated with sulfur for enhanced amidation efficiency

A thermally stable, fluorous sulfur-containing boronic acid catalyst has been developed and was shown to efficiently promote dehydrative condensation between carboxylic acids and amines under environmentally friendly conditions. The methodology can be applied to aliphatic, aromatic and heteroaromatic acids as well as primary and secondary amines. N-Boc protected amino acids were also successfully coupled in good yields with very little racemization. The catalyst could be reused four times with no significant loss of activity.

Chemical Wastes in the Peptide Synthesis Process and Ways to Reduce Them

In recent decades, a growing interest has been observed among pharmaceutical companies in producing and selling 80 FDA-approved therapeutic peptides. However, there are many drawbacks to peptide synthesis at the academic and industrial scales, involving the use of large amounts of highly hazardous coupling reagents and solvents. This review focuses on hideous and observant wastes produced before, during, and after peptide synthesis and proposes some solutions to reduce them.

Domino C-C/C-O bond formation: palladium-catalyzed regioselective synthesis of 7-iodobenzo[b]furans using 1,2,3-triiodobenzenes and benzylketones

A facile and efficient synthesis of 7-iodobenzo[b]furan derivatives via a highly regioselective tandem α-arylation/intramolecular O-arylation of 5-substituted-1,2,3-triiodobenzenes and benzylketones is described. Remarkably, the α-arylation coupling reactions initiate exclusively at the least sterically-hindered position of the triiodoarene, which results in a highly chemoselective transformation. The highest yields were observed in reactions between electron-poor 1,2,3-triiodoarenes and electron-rich benzylketones, yet the optimized reaction conditions were found to be tolerant to a wide range of different functional groups. This unprecedent synthesis of 7-iodobenzo[b]furans from 1,2,3-triiodobenzenes is scalable, general in scope, and provides easy access to valuable precursors for other chemical transformations.

Copper(i)-catalyzed regioselective Ullmann-type coupling of primary carbamates and 5-substituted-1,2,3-triiodobenzenes: facile synthesis of 2,3-diiodinated N-aryl carbamates

Mild, efficient, and unprecedented synthesis of 2,3-diiodinated N-aryl carbamates via highly regioselective Ullmann-type cross-coupling of 5-substituted-1,2,3-triiodobenzene and carbamate.