Recent Advances in Transition-Metal-Catalyzed (4+3)-Cycloadditions

Abstract

A (4+3)-cycloaddition combines a four-atom synthon and three-atom synthon to form seven-membered rings. In the past decade, many improvements have been made to this class of cycloaddition, including excellent diastereo- and enantioselectivities, both intra- and intermolecularly. Through the strategic use of transition-metal catalysts, acids, bases, and organocatalysts, it is possible to perform the cycloaddition on a variety of substrates, generating novel seven-membered rings. With these advances, (4+3)-cycloaddition has also been applied to the synthesis of biologically relevant compounds and natural products. We exclude the cycloadditions of cyclic dienes such as furan, pyrrole, cyclohexadiene or cyclopentadiene as Chiu, Harmata, Mascareñas­ and others have recently published thorough reviews on that topic. We will however discuss the recent additions (2009–2020) to the literature for the (4+3)-cycloadditions involving other types of four-atom synthons.1 Introduction2 Rhodium2.1 Cyclopropanation/Cope Rearrangement2.2 C–H activation3 Gold, Silver4 Copper5 Palladium, Platinum, Iridium6 Dual-Activation7 Conclusion

Recent Progress in Heterocycle Synthesis: Cyclization Reaction with Pyridinium and Quinolinium 1,4-Zwitterions

“…Seven-membered rings as integral subunits are ubiquitous in a wide variety of clinical drugs and bioactive natural products [ 61 , 62 , 63 ], and selectively synthesizing structurally diverse seven-membered rings remains an important pursuit in the field of organic synthetic chemistry [ 64 , 65 , 66 , 67 ]. The (3 + 4) cycloaddition reaction has attracted more and more attention for its diversity and high efficiency [ 68 , 69 , 70 , 71 ]. Formal (3 + 4) cyclization involving sulfur-based pyridinium 1,4-zwitterions has been used in the synthesis of seven-membered heterocyclic skeletons such as thiadiazepine, thiazepine, and oxathiepine.…”

Chemodivergence in Pd-catalyzed desymmetrization of allenes: enantioselective [4+3] cycloaddition, desymmetric allenylic substitution and enynylation

“…3 However, in contrast with well-developed [3+2] and [3+3] cycloadditions, [4+3] cycloadditions especially in a catalytic asymmetric manner, are under-developed. 4,5 Thus, developing new three-atom or four-atom synthons and designing new strategies for catalytic asymmetric [4+3] cycloaddition to construct seven-membered cyclic compounds, especially those which are difficult to access by existing methods, are highly desirable. In contrast with the previously reported studies focusing on the construction of seven-membered ring systems bearing central chirality , catalytic asymmetric [4+3] cycloaddition to construct seven-membered ring systems bearing axial chirality remains elusive.…”

Synthesis of Oxo-Bridged Dibenzoazocines through Ruthenium-Catalyzed [4 + 3]-Cycloannulation of Aza-ortho-quinone Methides with Carbonyl Ylides

“…Intermolecular [4 + 3] cycloaddition reactions play an important role in preparing medium-sized heterocycles due to their atom-economy and step-economy . Carbonyl ylides generated in situ from decomposition of diazo compounds and the trap of the metal carbene complex by a carbonyl moiety are highly reactive 1,3-dioples, which have been well employed in [3 + 2] cycloaddition reactions to synthesize oxacyclic systems (Scheme a) .…”