Pyridine-borane complexes were synthesized from 2-arylpyridines through an electrophilic aromatic borylation reaction with BBr(3). The intermediate 2-(2-dibromoborylaryl)pyridines were stable enough to be handled in air and served as the synthetic platform for variously substituted pyridine-borane complexes. This facile method would be useful for the synthesis of aza-π-conjugated materials having boron-nitrogen coordination.

A directed cross-aldol reaction of silyl enol ethers with carbonyl compounds, such as aldehydes and ketones, promoted by a Lewis acid, a reaction which is now widely known as the Mukaiyama aldol reaction. It was first reported in 1973, and this year marks the 40th anniversary. The directed cross-aldol reactions mediated by boron enolates and tin(II) enolates also emerged from the Mukaiyama laboratory. These directed cross-aldol reactions have become invaluable tools for the construction of stereochemically complex molecules from two carbonyl compounds. This Minireview provides a succinct historical overview of their discoveries and the early stages of their development.

No abstract

Reactions cleaving carbon-carbon bonds with the assistance of transition metals as the catalyst have provided various molecular transformations that are otherwise difficult to execute, opening a scenic avenue along organic synthesis. Construction of structural motifs like medium-sized carbocycles and chiral quaternary carbon centres have been set within an access of such paradoxical approaches in the past decade.

o-Alkylphenyl ketones undergo a C-C bond forming carboxylation reaction with CO2 simply upon irradiation with UV light or even solar light. The reaction presents a clean process exploiting light energy as the driving force for carboxylation of organic molecules with CO2.

Conventional organic synthesis has been mainly based upon the reactivities of π-bonds and polar σ-bonds. Carbon-carbon single bonds are nonpolar and generally far less reactive. Although they remain intact under most reaction conditions, it is possible to activate and cleave them if suitable organometallic compounds or metal catalysts are applied. Such C-C single bond cleavage reactions are attracting increasing attention in the context of synthetic chemistry because they provide a unique and more straightforward route from readily available substances to targets, while requiring significantly fewer steps. The present Perspective aims to exemplify the potential of metal-catalyzed C-C single bond cleavage for organic synthesis.

N-Sulfonyl-1,2,3-triazoles react with water in the presence of a rhodium catalyst to produce α-amino ketones in high yield. An intermediary α-imino rhodium(II) carbenoid undergoes insertion into the O-H bond of water. This transformation formally achieves 1,2-aminohydroxylation of terminal alkynes in a regioselective fashion when combined with the copper(I)-catalyzed 1,3-dipolar cycloaddition with N-sulfonyl azides.

During the preparation of the manuscript, different fields of the same sample for WGA immunofluorescence staining were mistakenly used to represent 2 distinct treatment groups on 2 occasions, in Figures 2 and 7, and some of the raw data for the earlier experiments were lost due to poor record keeping. All authors have agreed to retract the article. The authors sincerely apologize for any inconvenience this action has caused.