1995
DOI: 10.1039/c39950002457
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The scope and mechanism of a novel synthesis of 3,4-fused isoxazoles

Abstract: Thermal cyclisation of 2-nitrophenyl-and 3-nitrohetaryl-ethanoate derivatives in xylene is facilitated indirectly by 5 A molecular sieves affording an efficient general method for the construction of synthetically useful 3,4-fused isoxazoles; evidence for the mechanism of these novel heterocyclisation reactions is presented.Monocyclic isoxazoles are widely exploited1 through reductive ring scission as a valuable source of synthetically useful p-

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Cited by 12 publications
(6 citation statements)
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“…These compounds can be prepared either by the condensation of 4‐aminoisoxazole‐3‐carboxamides with ethyl orthoformate or through the ring contraction caused by the reduction of triazino[5,4‐d]pyrimidine 3‐oxides with stannous chloride . Heat treatment of 5‐nitropyrimidine ethanoate or iodine‐mediated ring closure of 5‐nitro‐6‐phenylethynyl‐pyrimidine affords pyrimidine‐fused isoxazoles as a result of intramolecular cyclization. At the same time, we have not encountered in the literature any references concerning the synthesis of 6,7‐dihydroisoxazolo[4,3‐d]pyrimidin‐5(4 H )‐ones.…”
Section: Resultsmentioning
confidence: 99%
“…These compounds can be prepared either by the condensation of 4‐aminoisoxazole‐3‐carboxamides with ethyl orthoformate or through the ring contraction caused by the reduction of triazino[5,4‐d]pyrimidine 3‐oxides with stannous chloride . Heat treatment of 5‐nitropyrimidine ethanoate or iodine‐mediated ring closure of 5‐nitro‐6‐phenylethynyl‐pyrimidine affords pyrimidine‐fused isoxazoles as a result of intramolecular cyclization. At the same time, we have not encountered in the literature any references concerning the synthesis of 6,7‐dihydroisoxazolo[4,3‐d]pyrimidin‐5(4 H )‐ones.…”
Section: Resultsmentioning
confidence: 99%
“…Preparation of substituted isoxazolo[4,3-d]pyrimidines 79 was accomplished on the basis of nitro derivatives 75 [54] obtained via interaction of ortho-chloronitropyrimidines and malonic ester. Heating of the compound 75 resulted in elimination of an alcohol molecule and formation of ketene 76 (Scheme 31).…”
Section: Formation Of Five-membered Ringsmentioning
confidence: 99%
“…127 The proposed initial step is the generation of a ketene, which cyclises to the intermediate from which carbon dioxide is eliminated. 3-Aminobenzoisoxazoles have hitherto been virtually unknown but two routes to derivatives of this class, one starting with 2-fluorobenzonitriles 128 and the other from 2-fluorobenzamides, 129 have been described.…”
Section: Isoxazoles Isothiazoles and Fused Analoguesmentioning
confidence: 99%