Synthesis of 1,2‐Dihydrocyclobuta[b]quinoline Derivatives from Isocyanophenyl‐Substituted Methylenecyclopropanes

Abstract

A new protocol to synthesize 1,2‐dihydrocyclobuta[b]quinoline derivatives from isocyanophenyl‐substituted methylenecyclopropanes via a formal insertion of isocyanide carbon into a C−C bond has been developed. The reaction proceeds smoothly in the presence of silver carbonate (5 mol%) upon heating in a highly atom economic manner and exhibits broad substrate scope, giving the desired products in moderate to excellent yields. Furthermore, several transformations of the obtained products have been also demonstrated.magnified image

Dimerization–cyclization reactions of isocyanoaryl-tethered alkylidenecyclobutanes via a triplet biradical mediated process

“…The suggested ionic reaction mechanism of isocyanoaryl-substituted alkylidenecyclopropane (ACP) 1′ is shown in Scheme 2 ( previous work). 8 Initially, the CvC double bond of ACP I′ was activated by Ag + ions to furnish an intermediate II′, which subsequently underwent an intramolecular nucleophilic attack to afford intermediate III′.…”

“…In 2017, our group reported a novel formal [3 + 1] cyclization reaction of isocyanoaryl-substituted alkylidenecyclopropanes for the synthesis of 1,2-dihydrocyclobuta [b]quinoline derivatives in moderate to excellent yields (Scheme 1, previous work). 8 We proposed that this cyclization reaction proceeded through an intramolecular nucleophilic attack of the isocyanide group to the CvC double bond, Ag ion elimination and cyclopropane ring expansion, furnishing 1,2-dihydrocyclobuta [b]quinoline derivatives. On the basis of this previous work, we envisaged that if isocyanoaryl-tethered alkylidenecyclobutanes are used as substrates to conduct the same reaction, the cyclobutane ring expansion could also be realized.…”

The Construction of Molecular Complexity from Functionalized Alkylidenecyclopropanes (FACPs)

“…By using isonitrile‐substituted FACPs 128 as substrates, we further developed a Ag‐catalyzed formal [3+1] cyclization reaction, thereby delivering diversified 1,2‐dihydrocyclobuta[ b ]quinoline derivatives 142 in good yields . The proposed mechanism is outlined in Scheme .…”

“…By using isonitrile-substituted FACPs 128 as substrates, we furtherd eveloped aA g-catalyzed formal [3+ +1] cyclization reaction, therebyd elivering diversified 1,2-dihydrocyclobuta[b]quinoline derivatives 142 in good yields. [35] The proposedm echanism is outlined in Scheme 26. The Ag catalystm ight simultaneously activate the alkylidenecyclopropane and isonitrile moieties to produce intermediate 143,w hich is in equilibrium with intermediate 144.T hen, ac onsecutive nucleophilic attack of Scheme22.…”

“…Ag-catalyzed formal [3+ +1] cyclization of isonitrile-substituted FACPs 128. [35] Scheme27. Palladium-catalyzed difluoromethylation and perfluoroalkylation of FACPs 146.…”