Recent Advances in the Construction of Fluorinated Organoboron Compounds.

Fluorinated organoboron compounds are important synthetic building blocks that combine the unique characteristics of a fluorinated motif with the versatile synthetic applications of organoboron moiety. This review article guides the research on fluorinated organoboron compounds mainly from four aspects in recent years: selective monodefluoroborylation of polyfluoroarenes and polyfluoroalkenes, selective borylation of fluorinated substrates, selective fluorination of organoboron compounds, and borofluorination of alkynes/olefins. In addition, this review will provide a necessary guidance and inspiration for the research on the valuable synthetic building block fluorinated organoboron compounds.

Base-promoted domino-borylation-protodeboronation strategy.

Since a nucleophilic sp2 boron species can be generated in situ under the combined action of an inorganic base, B2pin2 and methanol, research on base-promoted nucleophilic borylation of unsaturated compounds has attracted significant attention. A series of multi-borylated compounds, such as alkyl 1,2-bis(boronates), gem-diborylalkanes, and 1,1,2-tris(boronates), are constructed based on this strategy. These multi-borylated compounds can in turn undergo selective protodeboronation, creating a variety of useful boron-containing compounds. This Feature article documents the development of base-promoted domino-borylation-protodeboronation (DBP) strategies and their applications in organic synthesis.

Precise Construction of SCF2H or SeCF2H Groups on Heteroarenes Generated in Situ from CF3-Containing 1,3-Enynes.

A divergent strategy for precise construction of SCF2H or SeCF2H groups on heteroarenes generated in situ from CF3-containing 1,3-enynes was developed. Reactions of readily available 1,3-enynes with S8 and ClCF2H provided 3-SCF2H-4-CF3-thiophenes via a cascade thiophene construction/selective C3 position thiolation/difluoromethylthiolation process, as did a series of 3-SeCF2H-4-CF3-selenophenes by similar strategies. The plausible radical annulation process for the construction of the thiophene ring and difluorocarbene generated in situ was confirmed by experiment.

Synthesis of anti-vicinal diboronates from diarylethynes and B2pin2.

Anti-vicinal diboronates were fabricated from easily available diarylethynes and B2pin2 via a base-catalyzed domino-borylation-protodeboronation (DBP) strategy under transition-metal-free conditions. Under the standard conditions, reactants with a range of different classes of functional groups on the rings, such as MeO, MeS, CF3O, Me2N, TMS, I, Br, Cl, F, and the thiophene ring, were tolerated. Downstream transformation of the vicinal diboronates provided a facile pathway for obtaining vicinal diols by mild oxidation with NaBO3, and a new deuteriation technique was developed in order to acquire 1,2-diarylethanes-1,2-d2 and 1,2-diarylethanes-1,1,2,2-d4. The new deuteriation strategy developed in this study may provide a new research direction for deuteriation chemistry.

Base-Catalyzed Borylation/B-O Elimination of Propynols and B2pin2 Delivering Tetrasubstituted Alkenylboronates.

An efficient approach to tetrasubstituted alkenylboronates via a cascade borylation/B-O elimination of propynols and B2pin2 was disclosed. A series of tetrasubstituted alkenylboronates were readily furnished with this strategy in good yields, with further transformations leading to tetrasubstituted alkenes and ß-diketones demonstrating the synthetic potential of the alkenylboronates constructed by this strategy as versatile intermediates in organic synthesis.

Cu/Pd cooperatively catalyzed tandem intramolecular anti-Markovnikov hydroarylation of unsaturated amides: facile construction of 3,4-dihydroquinolinones via borylation/intramolecular C(sp3)-C(sp2) cross coupling.

An anti-Markovnikov hydroarylation of unsaturated amides via a Cu/Pd synergistically catalyzed cascade borylation/intramolecular sp2-sp3 cross-coupling has been disclosed. 3,4-Dihydroquinolinones, one type of important scaffold prevailing in pharmaceuticals and biologically active compounds, could be readily accessible with high regio-selectivity and high yields.

Pd-Catalyzed Regioselective 1,2-Difunctionalization of Vinylarenes with Alkenyl Triflates and Aryl Boronic Acids at Ambient Temperature.

A Pd-catalyzed highly regioselective 1,2-difunctionalization of vinylarenes is disclosed in which multisubstituted olefins are efficiently and conveniently constructed under ambient temperature with good compatibility and a broad substrate scope. Notably, a quarternary carbon center could be readily built up from 1,1-disubstituted styrenes, which are big challenges in the previous methods.

Diborane-Mediated Deoxygenation of o-Nitrostyrenes To Form Indoles.

A mild, transition metal-free, diborane-mediated deoxygenation of nitro groups was discovered that in situ generates nitrosoarene reactive intermediates. This new reactivity mode of B2pin2 was leveraged to construct indoles from o-nitrostyrenes through a reductive-cyclization reaction that exhibits a Hammett ρ-value of +0.97 relative to σpara values. Our new deoxygenation reaction is efficient, practical, and scaleable, enabling access to a broad range of indoles.