A general and unprecedented gold-catalyzed tandem dual heterocyclization reaction of enynones with 1,3,5-triazines has been developed, which provides bicyclic fused furans in high to excellent yields under mild reaction conditions. In addition, mechanistic studies indicate that the reaction goes through a stepwise [3+2+2]-cycloaddition of furanyl gold intermediate, which is generated from gold-catalyzed cyclization of enynone, with two molecules of formaldimines derived in situ from 1,3,5-triazine, instead of formal [4+3]-cycloaddition.

A gold-catalyzed cyclization/carbonylation cascade reaction of 1,6-diynes is reported. The reaction goes through 6-exo-dig and 6-endo-dig cyclizations in sequence, followed by hydration to provide the β,γ-unsaturated ketones with moderate to high yields under mild reaction conditions. This is the first example of intercepting the postulated 1,3-oxazine vinylgold intermediate with another pendant alkyne, which not only verifies the proposed mechanism but also provides the ketone products with cyclized 1,2,3,6-tetrahydropyridine or 3,6-dihydro-2H-pyran frameworks from corresponding diynes.

A copper-catalyzed novel carbene/alkyne metathesis cascade reaction with alkyne-tethered diazo compounds is described. The whole transformation features a dual-functionalization of alkyne to install one C═N and one C═C bond on each carbon with azide and diazo groups, respectively, in one reaction, which represents a practical synthetic alternative to the multisubstituted 4-carboxyl quinoline derivatives and with most of them in high to excellent yields.Keywords: alkyne functionalization; azide; carbene/alkyne metathesis; cascade reaction; diazo compound; quinoline

A general and unprecedented thermally induced formal [3 + 2] cycloaddition has been developed that provides a general access to fused lactam derivatives in high to excellent yields with broad substrate scope. In comparison with the reported metal-catalyzed carbene/alkynyl metathesis, this is the only example in this area under catalyst-free conditions with excellent selectivity. Mechanistic studies indicate that the 3H-pyrazole is the key intermediate in this cascade reaction, which is confirmed spectroscopically for the first time.

An efficient transition-metal-free fluoroarylation reaction of N-aryl diazoacetamides with NFSI (N-fluorobenzenesulfonimide) is described. This reaction directly provides 3-fluorooxindole derivatives in yields of 67–93% with high selectivity via a carbene-free process under mild reaction conditions.

The third-order nonlinear optical properties of a series of resonance benzo[a]phenoxazinium salts in acetic acid solution were studied using the Z-scan technique employing a Nd:YAG nanosecond laser at 532 nm. The compounds displayed strong reverse absorption with third-order nonlinear optical coefficients of 0.42–1.20 × 10−11 esu and second hyperpolarizabilities of 2.75–7.29 × 10−29 esu, respectively. Quantum chemical calculations showed that the compound with more stable highest occupied molecular orbital energy also displayed highest second hyperpolarizability.