Nickel-Catalyzed Umpolung Arylation of Ambiphilic α-Bromoalkyl Boronic Esters

A radical 1,4-aryl migration enables nickel-catalysed remote cross-electrophile coupling of β-bromo amino acid esters with vinyl triflates

A radical 1,4-aryl migration enabling a cross-electrophile coupling reaction toward remote transalkylation of N-benzyl alanine has been developed. In this strategy, with the occurrence of a radical-mediated Turce-Smiles rearrangement, key α-aminoalkyl radicals are generated. The as-formed α-aminoalkyl radical serves as a robust coupling partner for cross-electrophilic coupling with vinyl triflates, affording a series of olefin-tethered amino acid motifs.

Recent Advances in Radical Addition to Alkenylboron Compounds

The addition of carbon-centered radicals to alkenylboron compounds provides a useful method for the construction of organoboron reagents which are versatile reagents in chemical synthesis. While the first examples of this type or process appeared 70 years ago, until recently, attention to this type of reaction has been limited. A number of examples of this reactivity have been demonstrated recently, and strategies are emerging that allow for tuning the reagent structure in order to modulate reactivity. This review surveys recent advances in this class of reaction.

Decarboxylative Conjunctive Cross-coupling of Vinyl Boronic Esters using Metallaphotoredox Catalysis

The synthesis of complex alkyl boronic esters through conjunctive cross-coupling of vinyl boronic esters with carboxylic acids and aryl iodides is described. The reaction proceeds under mild metallaphotoredox conditions and involves an unprecedented decarboxylative radical addition/cross-coupling cascade of vinyl boronic esters. Excellent functional-group tolerance is displayed, and application of a range of carboxylic acids, including secondary α-amino acids, and aryl iodides provides efficient access to highly functionalized alkyl boronic esters. The decarboxylative conjunctive cross-coupling was also applied to the synthesis of sedum alkaloids.

Site-Selective 1,2-Dicarbofunctionalization of Vinyl Boronates through Dual Catalysis

A modular, site-selective 1,2-dicarbofunctionalization of vinyl boronates with organic halides through dual catalysis is described. This reaction proceeds under mild conditions and is characterized by excellent chemo- and regioselectivity. It thus represents a complementary new technique for preparing densely functionalized alkyl boron architectures from simple and accessible precursors.

Nickel-Catalyzed Regioselective Hydroalkylation and Hydroarylation of Alkenyl Boronic Esters

Metal hydride catalyzed hydrocarbonation reactions of alkenes are an efficient approach to construct new carbon-carbon bonds from readily available alkenes. However, the regioselectivity of hydrocarbonation remains challenging to be controlled. In nickel hydride (NiH) catalyzed hydrocarbonation, linear selectivity is most often obtained because of the relative stability of the linear Ni-alkyl intermediate over its branched counterpart. Herein, we show that the boronic pinacol ester (Bpin) group directs a Ni-catalyzed hydrocarbonation to occur at its adjacent carbon center, resulting in formal branch selectivity. Both alkyl and aryl halides can be used as electrophiles in this hydrocarbonation, providing access to a wide range of secondary alkyl Bpin derivatives, which are valuable building blocks in synthetic chemistry. The utility of the method is demonstrated by the late-stage functionalization of natural products and drug molecules, the synthesis of an anticancer agent, and iterative syntheses.

Rapid Access to Highly Functionalized Alkyl Boronates by NiH-Catalyzed Remote Hydroarylation of Boron-Containing Alkenes

The direct and selective functionalization of relatively simple and readily accessible precursors to produce highly functionalized alkyl boronates is a synthetically useful process. Herein we report a NiH-catalyzed remote hydroarylation process that can, through a synergistic combination of chain walking and subsequent cross-coupling, introduce an aryl group at the adjacent carbon atom of alkyl boronates under mild conditions. By means of a preliminary experiment with moderate enantioselectivity, it was shown that an asymmetric version could also be realized.

Merging Art and Science-The 53rd Bürgenstock Conference

For the 53rd time, the Bürgenstock Conference gathered some of the most gifted scientists and rising stars in organic, physical, and bioorganic chemistry. Orchestrated by Ilan Marek (President) and his successor, Véronique Gouverneur, the synergy between art and science took place in Brunnen, Switzerland, with a beatiful view over Lake Lucerne.