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A strategy for the synthesis of α-carboline derivatives from indole-3-carboxaldehydes and 3-aminocyclohex-2-enones under metal-free conditions has been developed. The combination use of phenyliodine (III) diacetate (PIDA) and benzoic acid could significantly facilitate the corresponding [3 ​+ ​3] annulation process. This newly developed strategy featured unextraordinary chemoselectivity, good functional group tolerance and the preservation of the carbonyl group of the ketone substrates, which offers the possibility for further transformation of the products.

An acetic acid-promoted C(sp3)-H functionalization of 2-methyl quinoline, enaminoesters and elemental sulfur for the synthesis of 3,4,5-trisubstituted isothiazoles under metal-free conditions has been developed. This approach provides viable access to various 5-(quinolin-2-yl)isothiazoles in moderate to good yields with good functional group tolerance. Moreover, the success of the gram-scale reaction gives this reaction a great potential application.

A CuBr2-catalyzed annulation of 2-bromo-N-arylbenzimidamide with selenium/sulfur powder for the synthesis of benzo[d]isoselenazole and benzo[d]isothiazole in generally good yields was investigated. This synthetic strategy features good substrate scope and functional group tolerance. Furthermore, the corresponding products could be converted into N-aryl indoles viarhodiumIII-catalyzed orthoC–H activation of the N-phenyl ring, providing an efficient approach for axial aromatic molecules.

We have reported a metal-free protocol for the synthesis of indenoquinolinones and 2-substituted quinolines via[4 + 2] cycloaddition reaction using readily available 2-aminobenzaldehydes and ketones as starting materials. Different quinoline derivatives can be selectively synthesized by changing the type of ketones. O2and dimethyl sulfoxide (DMSO) as co-oxidants play an important role in the synthesis of indenoquinolinones. This condensation/oxidation strategy involves the formation of C–N, C–C, and C–O bonds, with the advantages of high yields and a broad substrate range.

Myrosinase (Myr), as a unique β-thioglucosidase enzyme capable of converting natural and gut bacterial metabolite glucosinolates into bioactive agents, has recently attracted a great deal of attention because of its essential functions in exerting homeostasis dynamics and promoting human health. Such nutraceutical and biomedical significance demands unique and reliable strategies for specific identification of Myr enzymes of gut bacterial origin in living systems, whereas the dearth of methods for bacterial Myr detection and visualization remains a challenging concern. Herein, we present a series of unique molecular probes for specific identification and imaging of Myr-expressing gut bacterial strains. Typically, an artificial glucosinolate with an azide group in aglycone was synthesized and sequentially linked with the probe moieties of versatile channels through simple click conjugation. Upon gut bacterial enzymatic cleavage, the as-prepared probe molecules could be converted into reactive isothiocyanate forms, which can further act as reactive electrophiles for the covalent labeling of gut bacteria, thus realizing their localized fluorescent imaging within a wide range of wavelength channels in live bacterial strains and animal models. Overall, our proposed method presents a novel technology for selective gut bacterial Myr enzyme labeling in vitroand in vivo. We envision that such a rational probe design would serve as a promising solution for chemoprevention assessment, microflora metabolic mechanistic study, and gut bacterium-mediated physiopathological exploration.