Syntheses of spiro[indazole-3,3′-indolin]-2′-ones and spiro[indazole-3,3′-indolin]-2′-imines via 1,3-dipolar cycloadditions of arynes and studies on their isomerization reactions

Leveraging in situ N-tosylhydrazones as diazo surrogates for efficient access to pyrazolo-[1,5-c]quinazolinone derivatives

We developed a transition metal-free methodology for the construction of pyrazoloquinazolinone derivatives. The strategy involves a one-pot reaction wherein the N-tosylhydrazone and its corresponding diazo derivative are generated in situ, followed by an intramolecular 1,3-dipolar cycloaddition-ring expansion to provide the pyrazolo-[1,5-c]quinazolinone motif. This approach enables straightforward access to a diverse range of highly functionalized N-heterocyclic compounds in good yields (up to 92%).

Quinazolines annelated at the N(3)-C(4) bond: Synthesis and biological activity

This review covers article and patent data obtained mostly within the period 2013-2023 on the synthesis and biological activity of quinazolines [c]-annelated by five- and six-membered heterocycles. Pyrazolo-, benzimidazo-, triazolo- and pyrimido- [c]quinazoline systems have shown multiple potential activities against numerous targets. We highlight that most research efforts are directed to design of anticancer and antibacterial agents of azolo[c]quinazoline nature. This review emphases both on the medicinal chemistry aspects of pyrrolo[c]-, azolo[c]- and azino[c]quinazolines and comprehensive synthetic strategies of quinazolines annelated at N(3)-C(4) bond in the perspective of drug development and discovery.

Synthesis of Spiro[indazole-3,3′-indolin]-2′-ones and Indazolo [2,3-c]quinazolin-6(5H)-ones from Arynes and Isatin-Derived N-Tosylhydrazones

A formal (3+2) annulation reaction between isatin-derived N-tosylhydrazones and o-(trimethylsilyl)aryl triflates allows facile synthesis of spiro[indazole-3,3′-indolin]-2′-ones in high to excellent yields. Furthermore, indazolo[2,3-c]quinazolin-6(5H)-ones could be accessed from the same starting materials in one-pot fashion via an annulation/rearrangement pathway.

Recent advances in the synthesis of indole embedded heterocycles with 3-diazoindolin-2-imines

The preparations, reactivity and synthetic applications of 3-diazoindolin-2-imines, a valuable class of α-diazo amidines, are reviewed.