A highly regioselective and efficient base‐catalyzed intramolecular hydroalkoxylation of primary and secondary alkynyl alcohols was developed to afford 1,4‐oxaza heterocycles. Although the rates of cyclization for terminal alkynyl alcohols were significantly greater than those for internal ones, our method tolerated both terminal and internal alkynes. In addition, an unprecedented one‐pot hydroamination reaction was found to proceed with high chemo‐ and regioselectivity to form indole‐fused azlactones in the presence of base.

An expedient and metal-free synthetic route has been developed for the construction of tri- and tetrasubstituted imidazole derivatives via acid promoted multicomponent reaction methodology. The reaction proceeded smoothly with a range of functionalities to produce the imidazole scaffolds in good to excellent yields.

Novel bicyclic[1,2,3]triazoles (4, 7, 11, 15) have been synthesized using a one-pot metal free strategy with high structural diversity as photoprotective agents, and their effect on UVA-induced senescence in human dermal fibroblast cells (FB) and the associated mechanism are delineated. 11d plus UVA can induce a decrease in reactive oxygen species (ROS) production and senescence-associated β-galactosidase (SA-β-gal) activity but an increase in adenosine triphosphate (ATP) synthesis and mitochondrial membrane potential (ΔΨmt). The mRNA levels of six senescence-associated genes, matrix metalloproteinase-1 (MMP-1), was decreased, while elastin, procollagen I type I, fibronectin, COL1α1, and tissue inhibitor of metalloproteinase-1 (TIMP-1) were increased. 11d plus UVA also decreased MMP-1 and increased TIMP-1 protein levels. Additionally, the thickness of the murine dorsal skin and epidermis, by UVA, was decreased by topical 11d treatment. Our results indicate that bicyclic[1,2,3]triazoles protect UVA-induced senescence-like characteristics in FB cells, which may provide potential prevention against photoaging.

We have identified metal-free reaction conditions for the annulation/aerobic oxidative dehydrogenation of cyclohexanones with o-acylanilines to the corresponding acridine derivatives.

An iodine-promoted regioselective cyclization of N-propynyl/allyl amides with sulfonyl hydrazides has been developed for the synthesis of 5-methyl-arylsulfonyloxazoles and 5-methyl-arylthiooxazolines via sulfonylation and sulfenylation reactions. The notable features of this reaction are the formation of new C-S and C-O bonds, the broad functional group tolerance, and its applicability to alkyl sulfonyl hydrazides as well as internal alkynes.

A BF3-etherate-promoted cascade reaction of nitriles with 2-alkynylanilines is described. This method achieves the formation of two new C-N bonds through a reaction sequence of diazotization with t-BuONO, nucleophilic addition of the alkyne to the BF3-coordinated diazonium ion, followed by nitrile addition to the intermediary vinyl cation and hydrolysis. The method provides efficient and general access to a variety of 4-amido-cinnolines. Notable features of the method include its broad functional group tolerance and avoidance of transition metals.

I2-TBHP-catalyzed oxidative cross coupling of N-sulfonyl hydrazones with isocyanides has been realized for the synthesis of 5-aminopyrazoles through formal [4 + 1] annulation via in situ azoalkene formation. Notable features are the metal/alkyne-free strategy, C-C and C-N bond formation, atom economy, catalytic I2, broad functional group tolerance, good reaction yields, shorter time, and also applicability to one-pot methodology.

Alcohols and ethers were identified as sustainable methine sources for synthesizing quinazolinone and benzimidazole derivatives using a combination of TsOH·H2O/O2 and appropriate bis-nucleophiles for the first time.