Boron Trihalide Mediated Alkyne-Aldehyde Coupling Reactions: A Mechanistic Investigation

Haloboration: scope, mechanism and utility

Haloboration, the addition of B–X (X = Cl, Br, I) across an unsaturated moiety e.g., C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Y or C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Y (Y = C, N, etc.), is dramatically less utilised than the ubiquitous hydroboration reaction. However, haloboration of alkynes in particular is a useful tool to access ambiphilic 1,2-disubstituted alkenes. The stereochemical outcome of the reaction is easily controlled and the resulting products have proven to be valuable building blocks in organic synthesis and materials chemistry. This review aims at providing the reader with a brief summary of the historic development and of the current mechanistic understanding of this transformation. Recent developments are discussed and select examples demonstrating the use of haloboration products are given with a focus on the major areas, specifically, natural product synthesis and the development of boron-doped polycyclic aromatic hydrocarbons (B-PAHs).

Haloboration is a mostly overlooked technique, yet it is a powerful way of transforming alkynes stereoselectively into difunctionalised ambiphilic alkenes, which readily undergo a plethora of highly useful subsequent reactions.

Functional Poly(dihalopentadiene)s: Stereoselective Synthesis, Aggregation-Enhanced Emission and Sensitive Detection of Explosives

The development of polymeric materials with novel structures and unique properties and functionalities is of both academic and industrial significance. In this work, functional poly(dihalopentadiene)s were synthesized by boron trihalide-mediated multicomponent polymerization routes in a stereoselective manner. The polymerizations of tetraphenylethylene-containing diyne, BX₃ (X = Cl, Br) and p-tolualdehyde proceed smoothly in dichloromethane under mild conditions to afford high molecular weight poly(dihalopentadiene)s with a predominant (Z,Z)-configuration in moderate to good yields. The reaction conditions and the boron trihalide used were found to have great effects on the stereochemistry of the resulting polymer structures. The obtained poly(1,5-dihalo-(Z,Z)-1,4-pentadiene)s possess high thermal stability and good film-forming ability. Their thin films show high refractive index of 1.9007⁻1.6462 in a wide wavelength region of 380⁻890 nm with low optical dispersion. The polymers are weakly emissive in dilute solutions but become highly emissive upon aggregated, demonstrating a unique phenomenon of aggregation-enhanced emission. Their nanoaggregates in aqueous media can serve as sensitive fluorescent chemosensors for the detection of explosives with a superamplification effect and a low detection limit.

BCl3-mediated polycoupling of alkynes and aldehydes: a facile, metal-free multicomponent polymerization route to construct stereoregular functional polymers

BCl₃-mediated alkyne–aldehyde polymerization to stereoregular functional polymers in a facile, metal-free and multicomponent manner.

Stereoselective Synthesis of Trisubstituted Vinyl Bromides by Addition of Alkynes to Oxocarbenium Ions

We have developed an efficient method for the synthesis of (E)-trisubstituted vinyl bromides via a Friedel-Crafts-type addition of alkynes to oxocarbenium ions formed in situ from acetals. The success of this reaction relies on identification of MgBr2·OEt2 as both a Lewis acid promoter and bromide source. This reaction employs simple, inexpensive starting materials and proceeds under mild conditions to allow the preparation of a range of vinyl bromide products in high yields and E:Z selectivities. Furthermore, the vinyl bromide products also contain an allylic ether functional group. Both the vinyl bromide and allylic ether are effective handles for the elaboration of these useful synthetic intermediates.

AIE macromolecules: syntheses, structures and functionalities

A comprehensive review of macromolecules with aggregation-induced emission attributes is presented, covering the frontiers of syntheses, structures, functionalities and applications.