l-Proline catalyzed efficient one-pot three-component aza-Diels–Alder reactions on nitrostyrylisoxazoles: a facile synthesis of new isoxazolyl tetrahydroquinolines and isoxazolo[2,3-a]pyrimidines

Progress in the Chemistry of Tetrahydroquinolines

“…Rajanarendar and co-workers demonstrated a l -proline-catalyzed, one-pot, three-component aza-Diels–Alder reaction for the synthesis of isoxazolyl-tetrahydroquinolines 778/779 and isoxazolo­[2,3- a ]­pyrimidines starting from arylamines 775 , aldehydes 776 , and nitro­styryl­isoxazoles 777 (Scheme ). The reaction was highly efficient and gave high yields of the products diastereoselectively. In this organocatalytic protocol, the arylamines 775 reacted with l -proline-activated aldehydes 776 to give aldimines, which then reacted with nitro­styryl­isoxazoles 777 to furnish the desired products.…”

Phosphine-Catalyzed [3 + 2] Annulation of Morita–Baylis–Hillman Carbonates with Isoxazole-Based Alkenes

“…As one type of electron-deficient alkenes, 4-nitro-5-styrylisoxazoles, in which alkenes are installed on a 4-nitroisoxazole ring, have attracted much attention in various transformations for synthesis of isoxazole derivatives with structural diversity. They have extensively been applied in many annulation reactions such as 1,3-dipolar [3 + 2] cycloaddition of azomethine ylides, [3 + 2] cycloaddition of tosylmethyl isocyanide, N-heterocyclic carbene-catalyzed [3 + 2] and [4 + 2] annulation reactions of enals, l -proline-catalyzed one-pot three-component aza-Diels–Alder reactions, phase-transfer-catalyzed enantioselective cyclopropanation and [4 + 2] annulation, quinine-catalyzed [3 + 2] annulation of 3-isothiocyanato oxindoles, quinidine-derived thiourea-catalyzed [4 + 2] annulation of chromone-based oxindoles, cinchona-derived squaramide/base-catalyzed [2 + 2 + 2] annulation of β-dicarbonyl compounds and β-nitroalkenes, trienamine-mediated [4 + 2]-cycloaddition, and base-promoted [3 + 2] annulation of 1,4-dithiane-2,5-diol . With these synthetic reactions, diverse carbocyclic and heterocyclic compounds have been prepared.…”

A fast and highly efficient one-pot synthesis of novel isoxazolyl pyrido[2,3-b][1,4]oxazin-2(3H)-ones via Smiles rearrangement using task-specific ionic liquid [HMIm]BF4as green solvent

“…In our continuing efforts to utilize ionic liquids as environmentally attractive media, for the synthesis and catalytic processes, we have some interest in the synthesis of different heterocycles carrying isoxazole moiety (30)(31)(32). As a sequel to our investigations on multi-component synthesis (33)(34)(35)(36), as well as green synthesis, we, herein, report for the first time a simple and efficient one-pot synthesis of isoxazolyl pyrido-1,4-oxazinones from isoxazole amine, chloroacetyl chloride, and 2-chloro-3-hydroxypyridine via Smiles rearrangement promoted by the Brønsted acidic IL, 1-methyl imidazolium tetraflouroborate [HMIm]BF 4 , as a solvent and catalyst, under mild conditions. In view of this, our method has a merit, whereby the title compounds are being synthesized in a one-pot green method under mild conditions at ambient temperature in excellent isolated yields in short reaction time.…”