Catalytic [5 + 1]-Cycloadditions of Vinylcyclopropanes and Vinylidenes

Abstract

Polysubstituted cyclohexenes bearing 1,3 (meta) substitution patterns are challenging to access using the Diels–Alder reaction (the ortho–para rule). Here, we report a cobalt-catalyzed reductive [5 + 1]-cycloaddition between a vinylcyclopropane and a vinylidene to provide methylenecyclohexenes bearing all-meta relationships. Vinylidene equivalents are generated from 1,1-dichloroalkenes using Zn as a stoichiometric reductant. Experimental observations are consistent with a mechanism involving a cobaltacyclobutane formed from a [2 + 2]-cycloaddition between a cobalt vinylidene and a vinylcyclopropane.

NHC-Ni(II)-catalyzed cyclopropene-isocyanide [5 + 1] benzannulation

“…1d ), as well as the catalytic [2 + 2 + 2]/[4 + 2] cycloadditions of π-systems 45 – 49 . This finding also complements the vinyl cyclopropanes [5 + 1] reactions reported recently as well as those imidoyl insertions reactivities 50 – 52 . Unlike several other intramolecular ring-expanding strategies based on 1 for the syntheses of phenols and saturated N-cycles (e.g., cycloisomerizations of 1 bearing 3,3-dicarbonyl 53 and [4 + 3] cycloadditions of 1 bearing N-heteroaromatics 54 , respectively), our intermolecular strategy offers fused anilines and endocyclic dienes.…”

Cu(I)-Catalyzed Enantioselective [5 + 1] Cycloaddition of N-Aromatic Compounds and Alkynes via Chelating-Assisted 1,2-Dearomative Addition

“…Along with the development of atypical 1,3-dipole equivalents such as palladium-trimethylenemethane (Pd-TMM), donor- and acceptor-substituted cyclopropanes (D-A cyclopropanes), and conjugated metal-carbenoids, formal [3 + 3] cycloadditions have also been demonstrated as surrogates of Diels–Alder reactions. While [3 + 3] and [5 + 1] cycloadditions are alternative synthesis approaches to six-member rings, [5 + 1] cycloadditions have been less explored due to the lack of practical 5-atom synthons . Vinyl cyclopropanes (VCPs) and 1,4-enyne esters are worthy candidates, but the C1 partner compatible in such cycloaddition has been limited to carbon monoxide (Scheme a).…”

Catalytic Asymmetric Ring‐Opening Reactions of Unstrained Heterocycles Using Cobalt Vinylidenes

“…Previously, we showed that such intermediates can be captured by alkenes to form methylenecyclopropanes by a stepwise [2 + 2]-cycloaddition/CÀ C reductive elimination pathway. [15,16] When the substrate is 2,5-dihydrofuran, CÀ C reductive elimination does not occur. Instead, β-O elimination induces ring-opening, and the resulting vinylcobalt species undergoes transmetallation to form a vinylzinc product.…”