760190-61-2Relevant academic research and scientific papers
p-TSA-Based DESs as “Active Green Solvents” for Microwave Enhanced Cyclization of 2-Alkynyl-(hetero)-arylcarboxylates: an Alternative Access to 6-Substituted 3,4-Fused 2-Pyranones
Curti, Fabiola,Tiecco, Matteo,Pirovano, Valentina,Germani, Raimondo,Caselli, Alessandro,Rossi, Elisabetta,Abbiati, Giorgio
, p. 1904 - 1914 (2019/02/26)
In this paper, we describe the use of p-TSA based Deep Eutectic Solvents (DESs) as alternative environmental-friendly “active” solvents for the microwave-mediated synthesis of 6-substituted 3,4-fused 2-pyranones, and in particular isocoumarins, starting from 2-alkynyl-(hetero)arylcarboxylates. When the alkyne terminus bears a neutral or an electron-donating group (EDG), the reactions are fast, clean and highly regioselective, to give the 6-endo-dig cyclization products in good to excellent yields. For substrates bearing an electron-withdrawing group (EWG) on the alkyne end, the regioselectivity can be tuned by adding a small amount of silver(I) triflate as co-catalyst. DES was demonstrated to be reusable without loss of efficiency in terms of reaction yields. Based on experimental evidence and previous findings, two competitive mechanisms working simultaneously are proposed to explain the outcomes and the regioselectivity issues.
Base-catalyzed intramolecular heterocyclization of o-alkynylbenzhydrazides
Mikhailovskaya,Vasilevsky
scheme or table, p. 632 - 636 (2011/02/17)
The reaction of methyl o-(2-R-ethynyl)benzoates with hydrazine affords either fused 4-R-methylphthalazin-1-ones or 2-amino-3-R-methylideneisoindolin-1- ones. The latter are on treatment with KOH undergo recyclization into the corresponding 4-R-methylphthalazin- 1-ones.
