Lewis Acid-Relayed Singlet Oxygen Reaction with Enamines: Selective Dimerization of Enamines to Pyrrolin-4-ones.

Singlet oxygen (1O2)-mediated oxidation represents an attractive strategy for incorporation of oxygen atoms from air under mild and environmentally benign conditions. However, the 1O2 reaction with enamine suffers from fragmentation, leading to very unsuccessful transformation. Here, Lewis acid is introduced to intercept [2 + 2] or "ene" reaction intermediates of the 1O2 reaction and enables oxidative dimerization of enamines to produce pyrrolin-4-ones in good to excellent yields. Mechanistic studies reveal the formation of the imino ketone intermediate from the interaction of 1O2 and enamine, which is able to interact with Lewis acid, relaying the 1O2 reaction in enamine chemistry. For the first time, selective cross-dimerization of two different enamines is achieved. Due to the advantages of mild conditions, high chemoselectivity, and up to 99% yield, a promising strategy has been developed for synthesizing aza-heterocycles under ambient conditions, which can be further applied for the synthesis of imidazolone, quinoxaline, and highly functionalized imine.

Direct Arylation of Unactivated Alkanes with Heteroarenes by Visible-Light Catalysis.

The functionalization of aliphatic C-H bonds is both a major challenge and a desirable goal in organic synthesis. Here, we describe the successful arylation of unactivated alkanes with heteroarenes by using iridium polypyridyl complexes as the photocatalyst and persulfate as the HAT catalyst precursor under visible-light irradiation. This reaction features good functional group tolerance and broad scope with regard to both alkane and heteroarene substrates (37 examples), which allows direct access to alkyl-substituted N-heteroarenes, a key structural motif in natural products and bioactive molecules.

Radical Addition of Hydrazones by α-Bromo Ketones To Prepare 1,3,5-Trisubstituted Pyrazoles via Visible Light Catalysis.

A novel efficient tandem reaction of hydrazones and α-bromo ketones is reported for the preparation of 1,3,5-trisubstituted pyrazoles by visible light catalysis. In this system, the monosubstituted hydrazones show wonderful reaction activity with alkyl radicals, generated from α-bromo ketones. A radical addition followed by intramolecular cyclization affords the important pyrazole skeleton in good to excellent yields. This efficient strategy under mild conditions with wide group tolerance provides a potential approach to the 1,3,5-trisubstituted pyrazoles.

Continuous transform of transverse modes and transitional status analysis in solid-state laser.

With the agility of cavity control in solid-state-laser, we report abundant experimental phenomena of relatively complete Laguerre-Gaussian (LG) transverse multimodes transformation process including both stable and transitional status in a diode pumped Nd:YVO4 microcavity laser. Cavity structure, absorber, pump power, etc, synthetically have been found to contribute such abundant generation of patterns.