A Synthetic Protocol for the Construction of Chroman‐Spiroquinazolin(thi)one Framework via a Metal‐Free, Three‐Component, Domino, Double Annulations

Abstract

A three‐component domino approach for the synthesis of chroman‐spiroquinazolin(thi)ones is described. It involves a condensation of 2‐aminoacetophenones and iso(thio)cyanates followed by a hetero‐Diels‐Alder annulation with 2‐hydroxybenzyl alcohol derivatives. The reaction exhibits a broad substrate scope under a metal‐free catalytic condition.

Copper-Promoted Aerobic Oxidative [3+2] Cycloaddition Reactions of N,N-Disubstituted Hydrazines with Alkynoates: Access to Substituted Pyrazoles

“…On the basis of the experimental results presented above and previous reports, , a plausible mechanism is proposed in Scheme . Initially, 1-methyl-1-phenylhydrazine ( 1a ) was oxidized to radical intermediate 8 through a single-electron oxidation and deprotonation process.…”

Efficient synthesis of spiro diheterocycles via multi-component dicyclization reaction

“…Based on the previous reports, 13,14 a plausible mechanism for this in situ cyclization–spiroannulation strategy is proposed (Scheme 4). At first, 2′-aminoacetophenone ( 1 ) reacts with isocyanate ( 2 ) to generate intermediate E , which undergoes a rapid intramolecular cyclization to form intermediate F .…”

“…Based on our continuing interest to construct spirocycles, 13 we envision the reaction of 2′-aminoacetophenones and isocyanates, which can form quinazolinones by an in situ cyclization, followed by spiroannulation with 1,4-benzoquinones to build five-membered oxaspiros in one pot which contain a key tetrasubstituted carbon (Scheme 1c).…”

I2-mediated coupling of quinazolinone enamines with 2-aminopyridines: a new strategy to access spiroquinazolinones

“…In view of their interesting properties, great progress has been made in the architecture of the spirocyclic quinazolinone frameworks. 24 We recently devoted efforts to the construction of spiroquinazolinones from quinazolinone enamines by harnessing the intrinsic reactivity of these enamines with 2-aminobenzaldehydes, 25 2-hydroxybenzyl acetates, 26 N -methylanilines 27 and N -phenylglycines 28 (Scheme 1b). In order to expand the scope of reacting partners with enamines and inspired by the advantages of the umpolung strategy, in the current work we developed an I 2 -mediated umpolung at the beta-position of quinazolinone enamines with 2-aminopyridines for the synthesis of spiroquinazolinones (Scheme 1c).…”