Reductive Ring Opening of Arylcyclopropanecarboxamides Accompanied by Borylation and Enolate Formation

Reductive anti-Dizincation of Arylacetylenes

Arylacetylenes undergo anti-1,2-dizincation to afford trans-1,2-dizincioalkenes. The process employs sodium dispersion as a reducing agent and zinc chloride TMEDA complex as a reduction-resistant zinc electrophile. This reductive anti-dizincation contrasts with the conventional additive syn-dimetalation like silylzincation. The resulting dizincated alkenes undergo the cross-coupling to yield multi-substituted alkenes stereoselectively.

Donor-Acceptor Cyclopropanes: Activation Enabled by a Single, Vinylogous Acceptor

A novel class of highly activated donor-acceptor cyclopropanes bearing only a single, vinylogous acceptor is presented. These strained moieties readily undergo cycloadditions with aldehydes, ketones, thioketones, nitriles, naphth-2-ols and various other substrates to yield the corresponding carbo- and heterocycles. Diastereocontrol can be achieved through the choice of catalyst (Brønsted or Lewis acid). The formation of tetrahydrofurans was shown to be highly enantiospecific when chiral cyclopropanes are employed. A series of mechanistic and kinetic experiments was conducted to elucidate a plausible catalytic cycle and to rationalize the stereochemical outcome.

Asymmetric C(sp3)-H borylation: an update

Chiral organoboronates have emerged as a key intermediate in the development of pharmaceuticals and materials science. Therefore, several attempts have been made to design various synthetic methods to easily furnish these compounds during the past few decades. Inter alia, asymmetric catalysis has been increasing rapidly as a viable, practical and beneficial strategy for their preparation. In this respect, recent years have witnessed significant progress in aliphatic C-H borylation as the generated carbon-boron bonds are largely utilized to produce other carbon-carbon, carbon-nitrogen and carbon-oxygen bonds. This review presents a detailed overview and analysis of transition metal-catalyzed asymmetric C(sp³)-H borylation strategies. Overall, it assembles all the recent developments in this particular synthetic avenue up to March 2022.