Photochemistry of 3-alkoxychromones: photocyclisation of 2-aryl-6-chloro-3-{(thiophen-2-yl)methoxy}chromones

Kamboj, Ramesh C.; Berar, Urmila; Berar, Surinder; Siddiqui, Zeba N.; Gupta, Satish C.

doi:10.1590/s0103-50532010000200012

Cited by 5 publications

(5 citation statements)

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“…the 2′-and 6′-positions of the methoxyphenyl moiety, and (ii) to observe the effect of the propynyloxy group on photoproduct formation in comparison to other functionalities. 31 Irradiation of 5(a-d) in methanol with pyrex-filtered light from a 125 W Hg UV lamp under an N 2 atmosphere furnished two new compounds 6(a-d) and 7(a-d) in each case, as indicated by the thin layer chromatographic examination of their reaction mixtures (Scheme 2). The removal of solvent under reduced pressure and the chromatographic separation of photolysate with increasing proportions of ethyl acetate in ethyl acetate-petroleum ether yielded the xanthenones 6 (35-45%) and the dealkoxylated chromenones 7 (20-24%) as the photoproducts, approximately in the ratio 2 : 1, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…[23][24][25][26][27][28][29] In view of these and our continuous effort in developing the photochemistry of such molecules, in the present paper we wish to report the results of our investigations on the photolysis of some 4H-chromen-4-ones bearing the propynyloxy moiety at the 3-position and the 3-methoxyphenyl moiety at the 2-position, with the motive to determine the regioselective photocyclisation and other reactions, as elicited earlier in other similar molecules. [15][16][17][30][31][32]…”

Section: Introductionmentioning

confidence: 99%

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Phototransformation of 3-alkoxychromenones: regioselective photocyclisation and dealkoxylation

Khanna

Dalal

Kumar

et al. 2015

Photochem Photobiol Sci

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The phototransformation of some 2-(3-methoxyphenyl)-4H-chromen-4-ones bearing a propynyloxy moiety at the 3-position has been described. On photolysis with pyrex-filtered UV light from a Hg lamp (125 W), these chromenones produced a major amount of 5-ethynyl-2-methoxy-6-oxa-benzo[5,6-c]xanthen-7-ones consisting of an exotic tetracyclic scaffold. These photoproducts have been envisioned to be produced through regioselective ring closure at the 6'-position of the 2-(3'-methoxy)phenyl moiety of the initially formed 1,4-biradical via a γ-H abstraction mechanism. No product whatsoever was observed through ring closure at the 2'-position. This behaviour has been found to be in accordance with the directive influence observed in free radical aromatic substitutions. This regioselective photocyclisation is further supported by calculations made from 3D structures (MM2 program). In addition, during the irradiation of these substrates, 2-(3-methoxyphenyl)-4H-chromen-4-ones were also realised through dealkoxylation. The structures of the substrates and photoproduct(s) have been determined by their spectroscopic (IR, NMR, mass spectrometry) studies.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Phototransformation of 3-alkoxychromenones: regioselective photocyclisation and dealkoxylation

Khanna

Dalal

Kumar

et al. 2015

Photochem Photobiol Sci

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“…Some results (Kamboj et al, 2010) have also been reported upon the photolysis of 2-aryl-6-chloro-3-{(thiophen-2-yl)methoxy}chromones 53(a-d) and 54(a-b) in a Pyrex filtered light from a 125 W Hg vapor lamp under nitrogen atmosphere (Scheme 13). The major interest in this study was to investigate the effect of thiophene ring at the 3-alkoxy group upon photoproduct formation and also to investigate the possibility of any photo-transposition.…”

Section: (A-e)mentioning

confidence: 96%

Photochemical studies: Chromones, bischromones and anthraquinone derivatives

Yusuf

Solanki

Jain

et al. 2019

Arabian Journal of Chemistry

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Photochemical reaction is a chemical reaction initiated by the absorption of energy in the form of light resulting in different types of reaction. Chromones, bischromones and anthraquinones are the bichromophoric molecules which contain the carbonyl group and double bond in conjugation. Photochemical reactions of these compounds result in the formation of such molecules which are not obtained via conventional methods. This review article describes the photochemical transformations of chromones, bischromones and anthraquinone derivatives and here main emphasis has been laid upon the intramolecular photochemical H-abstraction reactions that provide many exotic heterocyclics as the final photoproducts. ª 2014 Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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“…1,4‐Biradicals generated upon photo‐irradiation of 2‐aryl‐3‐{(thiophen‐2‐yl)methoxy}chromones 83 produced various angular tetracyclic products i. e. the thienoxanthenones 84 and 85 bearing the thienyl group (Scheme ). The dehydrogenation and ring contraction products 85 and 86 respectively were also observed depending upon the electron density on the 2‐aryl ring …”

Section: Photochemical Synthesis Of Oxaxanthenonesmentioning

confidence: 98%

“…The angular tetracyclic xanthenone 54 and 55 products bearing the thienyl group were generated upon photo‐irradiation of 2‐aryl‐3‐{(thiophen‐2‐yl)methoxy} chromones 53 (Scheme ) in dry methanol …”

Section: Photochemical Synthesis Of Oxaxanthenonesmentioning

confidence: 99%

Synthesis of Xanthenones: A Review

et al. 2016

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Xanthenones constitute one of the most important classes of the naturally occurring organic compounds produced by many microorganisms. They exhibit many biological activities e. g., antibacterial, analgesics, antipyretics, cofactors etc. Structurally, these are the linear tricyclic compounds usually having O‐heteroatom and carbonyl group. The xanthenone scaffold can be considered as a privileged structure as a lead for the search of new bioactive molecules. Being of pervasive importance, their synthesis by conventional thermal methods has been the subject of many studies. The recent strategies in synthetic organic chemistry concerning the synthesis of novel organic compounds having diverse applications mainly aims at improvement in atom as well as cost efficiency, avoidance of toxic reagents, and reduction in waste. In this context, photochemical reactions are relevant both from economical as well as from ecological point of view and also obey the demands of “green chemistry” or of an “ideal synthesis”. This article presents a review on the synthetic methodologies of the xanthenones‐ thermal (2012 onwards) and photochemical in addition to our own work on their synthesis.

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Photochemistry of 3-alkoxychromones: photocyclisation of 2-aryl-6-chloro-3-{(thiophen-2-yl)methoxy}chromones

Cited by 5 publications

References 25 publications

Phototransformation of 3-alkoxychromenones: regioselective photocyclisation and dealkoxylation

Phototransformation of 3-alkoxychromenones: regioselective photocyclisation and dealkoxylation

Photochemical studies: Chromones, bischromones and anthraquinone derivatives

Synthesis of Xanthenones: A Review

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