2008
DOI: 10.3998/ark.5550190.0010.806
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The photochemistry of some pyranopyrazoles

Abstract: Irradiation of 1,3,6-trimethylpyrano [2,3-c] pyrazole-4 (1H)-one (1) or 3,6-dimethyl-1-phenylpyrano [2,3-c]pyrazole-4-(1H)-one (2) in acetonitrile solution at 254 nm resulted in the formation of the cis-head-to-tail [2+2] dimers 5 or 13 respectively. When the irradiation was carried out in ethanol solvent 1 or 2 underwent dimerization to yield 5 or 13 respectively and also photocleavage to provide ethyl 5-hydroxy-1,3-dimethyl-1H-pyrazole-4-carboxylate (10) or ethyl 5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-ca… Show more

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Cited by 5 publications
(5 citation statements)
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“…The regioselectivity could be completely reverted if the reaction was performed in the solid state . A diastereoselective [2 + 2] photodimerization was achieved with chiral amides. , The related [2 + 2] photodimerization of pyrano­[2,3- c ]­pyrazole-4-(1 H )-ones was studied by Pavlik et al, and the [2 + 2] photodimerization of 5-substituted 2-styryl-4-pyrones was investigated by Jakopčić and co-workers …”
Section: Direct Excitation and Sensitizationmentioning
confidence: 97%
See 1 more Smart Citation
“…The regioselectivity could be completely reverted if the reaction was performed in the solid state . A diastereoselective [2 + 2] photodimerization was achieved with chiral amides. , The related [2 + 2] photodimerization of pyrano­[2,3- c ]­pyrazole-4-(1 H )-ones was studied by Pavlik et al, and the [2 + 2] photodimerization of 5-substituted 2-styryl-4-pyrones was investigated by Jakopčić and co-workers …”
Section: Direct Excitation and Sensitizationmentioning
confidence: 97%
“…488 A diastereoselective [2 + 2] photodimerization was achieved with chiral amides. 490,491 The related [2 + 2] photodimerization of pyrano[2,3-c]pyrazole-4-(1H)-ones was studied by Pavlik et al, 492 and the [2 + 2] photodimerization of 5-substituted 2styryl-4-pyrones was investigated by Jakopcǐćand co-workers. 493 In some cases, the carbonyl group of [2 + 2] photocycloaddition products may give rise to further photoinduced reactions.…”
Section: -Cyclopentenonesmentioning
confidence: 99%
“…Pyranopyrazoles with fused oxygen heterocycle (such as pyran) and nitrogen heterocycle (such as pyrazole) play a critical role in agrochemicals through their bactericidal, insecticidal, herbicidal, acaricidal and fungicidal properties. 71 They are also used as UV-light absorbers due to their dimer-formation property under UV-light irradiation, 72 and show numerous biological and pharmacological properties. 71 b ,73 The pyrano[2,3- c ]pyrazole-based compounds are among the four most studied pyranopyrazoles, including pyrano[3,2- c ]pyrazole, pyrano[3,4- c ]pyrazole and pyrano[4,3- c ]pyrazole, which have been found in a substantial number of synthetic and natural molecules.…”
Section: Multicomponent Reactionsmentioning
confidence: 99%
“… 15 Some 2-amino-4 H -pyrans can be used as photoactive materials 16 as they can undergoes dimerization upon UV irradiation, therefore they can act as UV absorbers. 17 Furthermore, these compounds are used as cosmetics and pigments. 18 Fig.…”
Section: Introductionmentioning
confidence: 99%