Search

In this paper, we report a gold(I)‐catalyzed cascade cyclization of N‐ or O‐nucleophile tethered‐vinylidenecyclopropanes (VDCPs), resulting in the synthesis of pyrrole, furan, pyrrolidine, and piperidine skeletons in 30%‐98% yields. Depending on the carbon chain length connecting the nucleophile and VDCPs, two reaction pathways are available, leading to different products. Both α‐amino VDCPs and α‐hydroxyl VDCPs, where nucleophiles and VDCPs are connected by a methylene group, undergo intramolecular nucleophilic addition and aromatization, followed by ring‐opening of the cyclopropane unit to produce substituted pyrroles and furans. By extending the chain length to three or four carbons, it becomes possible to form pyrrolidines and piperidines with a cyclobutene moiety via ring expansion of the cyclopropane unit, accompanied by gold carbene induced vinylogous nucleophilic addition. [ABSTRACT FROM AUTHOR]

A cascade cyclization from Weinreb amide‐tethered methylenecyclopropanes and alkynes has been disclosed in this paper, which extends the umpolung ring opening of methylenecyclopropanes, giving a synthetic approach for the construction of polycyclic cyclopenta[b]naphthalenol framework. In the protocol, four carbon‐carbon bonds and two carbocycles are formed without the use of transition metals, providing a tool for constructing the structure‐related polycyclic compounds. [ABSTRACT FROM AUTHOR]

Employing silver/rhodium relay catalysis strategy, an intramolecular electrophilic cyclization and C−H activation followed by cascade hydrogenation and reductive amination has been developed. The acylmethylated isoquinoline derivatives could be afforded with broad substrate scope in 23–88% yields, which could be further transformed to the core skeleton of hexahydrodibenzo[a,g]quinolizine as drug‐candidates. Moreover, this reaction was achieved in a gram‐scale. A reasonable reaction mechanism has been proposed based on a series of control and KIE experiments. [ABSTRACT FROM AUTHOR]

A phosphine‐catalyzed intermolecular annulation reaction of functionalized ortho‐aminoacetophenones with alkynones has been disclosed in this paper. A variety of 2‐alkynylquinolines and benzo‐fused indolizine were selectively afforded in moderate to good yields at different reaction temperatures and with different phosphine catalysts via the in situ generated zwitterionic intermediate derived from alkynone and phosphine. [ABSTRACT FROM AUTHOR]

Abstract: A facile synthesis of benzonitriles via a base‐promoted tandem cyclization reaction of α,β‐unsaturated enones having electron‐withdrawing group (EWG) and 2‐acyl‐acrylonitriles was developed. This new synthetic method to access benzonitriles is suitable for a wide range of substrates. A plausible reaction mechanism is proposed on the basis of previous literature and our own investigations. [ABSTRACT FROM AUTHOR]

In this paper, we disclose a novel strategy for the phosphine-catalyzed cycloaddition/SN2 substitution domino reaction, giving functionalized O-bridged benzoazepine and benzoxazepine derivatives in moderate to good yields. Changing the N-H protecting group of ortho-aminotrifluoroacetophenone derivatives gave different bridged-ring products in one step. [ABSTRACT FROM AUTHOR]

A new zwitterion generated from different electron-deficient alkenes and phosphines has been designed and its reactivity was explored. We demonstrated that this new zwitterion directed a novel [2+1+2] cycloaddition reaction between vinylpyridines and isatin-derived electron-deficient alkenes, affording spirocyclopenteneoxindole derivatives containing three stereocenters in moderate to good yields with good diastereoselectivities. A plausible mechanism has been proposed relying on preliminary mechanistic investigations and supported by theoretical calculations. [ABSTRACT FROM AUTHOR]

An effective one-pot procedure for the synthesis of phenanthridine derivatives containing N- or O-heterocycles has been developed through a two-step rhodium-catalyzed [2+2+2] cycloaddition and gold-catalyzed heterocyclization under mild conditions. The substrate scope has been investigated and a plausible reaction mechanism has been proposed on the basis of control experiments and previous literature reports. [ABSTRACT FROM AUTHOR]

The first highly enantioselective formal [4+2] tandem cyclizations between isatylidenemalononitriles and activated dienes catalyzed by bifunctional chiral phosphine catalysts have been developed, yielding multistereogenic spirocyclic oxindoles in high yields and excellent optical purity. This reaction is accomplished via a tandem Rauhut-Currier/Michael/Rauhut-Currier reaction sequence. [ABSTRACT FROM AUTHOR]

A novel phosphine-promoted intramolecular cyclization of dicyclopropenones 1 has been described in this contribution. A variety of 2,3-dihydro-1 H-indene-4,6-diol derivatives 2 and hexahydropentalen-2-one derivatives 3 were obtained selectively in moderate to good yields under mild conditions through different phosphine-promoted reactions. [ABSTRACT FROM AUTHOR]

The catalytic asymmetric [4+2] annulations of isatins with but-3-yn-2-one catalyzed by the Cinchona alkaloids-derived oragnocatalyst (DHQD)2PHAL have been developed in the presence of 3.0 equivalents of D-diethyl tartrate in the mixed solvent (diphenyl ether/diethyl ether=1/1) or a slightly modified one, affording the corresponding substituted spiro[indoline-3,2′-pyran]-2,4′(3′ H)-diones in good to excellent yields with high enantioselectivities under mild conditions. [ABSTRACT FROM AUTHOR]

A novel Cinchona alkaloid-derived organocatalyst having stronger hydrogen-bonding donors that catalyzes the asymmetric [3+2] cycloaddition of 3-isothiocyanatooxindoles with allenic esters or 2-butynedioic acid diesters has been developed, affording functionalized spirooxindole derivatives in high yields along with good to excellent enantioselectivities under mild conditions. We also found that by changing the ratio of the substrates, different spirooxindole derivatives could be obtained in high yields along with good to excellent enantioselectivities. [ABSTRACT FROM AUTHOR]