Cleavage of Carbon–Carbon σ-Bonds of Four-Membered Rings

Abstract

This article reviews synthetic transformations involving cleavage of a carbon− carbon bond of a four-membered ring, with a particular focus on the examples reported during the period from 2011 to the end of 2019. Most significant is the progress of catalytic reactions involving oxidative addition of carbon−carbon bonds onto transition metals or β-carbon elimination of transition metal alkoxides. When they are looked at from synthetic perspectives, they offer unique and efficient methods to build complex natural products and structures that are difficult to construct by conventional methods. On the other hand, β-scission of radical intermediates has also attracted increasing attention as an alternative elementary step to cleave carbon−carbon bonds. Its site-selectivity is often complementary to that of transition metalcatalyzed reactions. In addition, Lewis acid-mediated and thermally induced ring-opening of cyclobutanone derivatives has garnered renewed attention. On the whole, these examples demonstrate unique synthetic potentials of structurally strained four-membered ring compounds for the construction of organic skeletons.

Rhodium-catalysed selective C–C bond activation and borylation of cyclopropanes

“…1B ). 13 Inspired by the success of directed borylation of alkenes and alkanes, we envisioned that the borylation of CPAs by chelation-assisted C–C bond activation 14 could provide a unique opportunity to access amino-containing boronates as potent protease inhibitors. 15 During the preparation of this paper, Yamaguchi and Yokogawa reported a related transformation achieved by C–C hydroboration of CPAs using an iridium catalyst and t Bu-Quinox as the ligand ( Fig.…”

Recent Advances on Synthetic Methodology Merging C–H Functionalization and C–C Cleavage

“…As mentioned in the introductory section of this review, the release of the strain of carbocyclic structures is one of the driving forces that can promote the cleavage of C–C bonds [ 26 ], generating intermediates of different nature depending on the experimental conditions which can further evolve intra- or intermolecularly to afford new organic scaffolds. This section presents recent progress carried out on the different approaches where the functionalization of a C–H bond is achieved through the use of cyclopropyl and cyclobutyl scaffolds [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ].…”

“…Tertiary alcohols bearing strained rings such as cyclopropanol and cyclobutanol have been widely used in strategies involving transition-metal catalyzed C–C cleavage [ 38 , 40 , 41 ]. In this regard, Li et al tackled the synthesis of 2-substituted quinolines 145 through the Rh(III)-catalyzed C–H activation of imidamide substrates 143 and cross-coupling with cyclopropanols ( Scheme 18 ) [ 67 ].…”

Oxime‐Derived Iminyl Radicals in Selective Processes of Hydrogen Atom Transfer and Addition to Carbon‐Carbon π‐Bonds

“…[64,65] Acyclic iminyl radicals are characterized by reactions involving 1,n-hydrogen atom transfer (HAT, n = 5 in most cases, Scheme 1,b) or the intramolecular addition of iminyl radical to the C=C bond (Scheme 1, c). Synthetic applications of O-substituted oximes as precursors of iminyl radicals were recently summarized in several reviews, [66][67][68][69][70][71][72][73] but in these papers attention was focused mainly on ring-opening reactions of cyclic iminyl radicals (Scheme 1, a) and in part on addition reactions (Scheme 1, c). Only a few selected examples of the wide variety of intramolecular additions of iminyl radical to carbon-carbon π-bonds and iminyl radical mediated HAT processes were covered in the reviews devoted to hydroxylamine derivatives as nitrogen-radical precursors [74] and remote CÀ H functionalization by intramolecular HAT.…”