Condition-Dependent Selective Synthesis of Indolo[1,2-c]quinazolines and Indolo[3,2-c]quinolines from 2-(1H-Indol-2-yl)anilines and Sulfoxonium Ylides

Synthesis of CF3-Isoquinolinones and Imidazole-Fused CF3-Isoquinolinones Based on C-H Activation-Initiated Cascade Reactions of 2-Aryloxazolines

Presented herein are novel syntheses of CF3-isoquinolinones and imidazole fused CF3-isoquinolinones based on the cascade reactions of 2-aryloxazolines with trifluoromethyl imidoyl sulfoxonium ylides. The formation of CF3-isoquinolinone involves an intriguing cascade process including oxazolinyl group-assisted aryl alkylation through C(sp2)-H bond metalation, carbene formation, migratory insertion, and proto-demetalation followed by intramolecular condensation and water-promoted oxazolinyl ring-scission. With this method, the isoquinolinone scaffold tethered with valuable functional groups was effectively constructed. By taking advantage of the functional groups embedded therein, the products thus obtained could be readily transformed into imidazole-fused CF3-isoquinolinones or coupled with some clinical drugs to furnish hybrid compounds with potential applications in drug development. In general, the developed protocols feature expeditious and convenient formation of valuable CF3-heterocyclic skeletons, broad substrate scope, and ready scalability. In addition, studies on the activity of selected products against some human cancer cell lines demonstrated their potential as lead compounds for the development of novel anticancer drugs.

Chameleonic Reactivity of Imidoyl Sulfoxonium Ylides: Access to Functionalized Pyrroles and Dihydro-pyridines

We have found a chameleonic reactivity of imidoyl sulfoxonium ylides. On the one hand, imidoyl sulfoxonium ylides react with electron-deficient reagents, such as alkynyl esters, to lead to the formation of 1,2-dihydro-pyridines. The methyl group attached to the sulfur atom acts as a methylene donor. On the other hand, imidoyl sulfoxonium ylides react with pyridinium 1,4-zwitterionic thiolates, which leads to the formation of functionalized pyrroles. Both transformations feature mild reaction conditions and good functional group tolerance.

P(III)-Mediated Formal Reductive N-H Bond Insertion Reaction of Hydrazones to α-Keto Esters

A diazo-, metal-, and base-free multi-substituted hydrazone synthesis via a formal reductive N-H bond insertion reactions of hydrazones to α-keto esters has been developed. The protocol features a broad substrate scope and good functional group tolerance, providing N-H bond insertion products in moderate to excellent yields. Moreover, P(III)-mediated N-H functionalization of pharmaceutical containing hydrazone moiety was also successfully achieved.

Stereoselective Synthesis of 12-Tetrazolyl Substituted (E)-5H-Quinazolino[3,2-a]quinazolines via Sequential Ugi-Azide/Staudinger/aza-Wittig/Addition/Ag(I)-Catalyzed Cyclization

A new efficient and stereoselective synthesis of 12-tetrazolyl substituted (E)-5H-quinazolino[3,2-a]quinazolines via sequential Ugi-azide/Staudinger/aza-Wittig/addition/Ag(I)-catalyzed cyclization was developed. The four-component reactions of 2-azidobenzaldehyde, 2-(alkynyl)benzenamine, isocyanide, and trimethylsilyl azide gave Ugi-azide intermediates, which were subsequently treated with triphenylphosphine and isocyanate to produce 12-tetrazolyl substituted (E)-5H-quinazolino[3,2-a]quinazolines in the presence of Ag(I) catalyst and K₂CO₃.