- Synthesis and anticancer activities of novel guanylhydrazone and aminoguanidine tetrahydropyran derivatives
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In this paper we present the convenient syntheses of six new guanylhydrazone and aminoguanidine tetrahydropyran derivatives 2-7. The guanylhydrazone 2, 3 and 4 were prepared in 100% yield, starting from corresponding aromatic ketones 8a-c and aminoguanidi
- Silva, Fábio Pedrosa Lins,Dantas, Bruna Braga,Martins, Gláucia Veríssimo Faheina,De Araújo, Demétrius Ant?nio Machado,Vasconcellos, Mário Luiz Araújo De Almeida
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- Trans-selective rhodium catalysed conjugate addition of organoboron reagents to dihydropyranones
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The selective synthesis of 2,6-trans-tetrahydropyran derivatives employing the rhodium catalysed addition of organoboron reagents to dihydropyranone templates, derived from a zinc-catalysed hetero-Diels-Alder reaction, is reported. The addition of both arylboronic acids and potassium alkenyltrifluoroborates have been accomplished in high yields using commercially-available [Rh(cod)(OH)]2 catalyst. The selective formation of the 2,6-trans-tetrahydropyran stereoisomer is consistent with a mechanism involving alkene association and carbometalation on the less hindered face of the dihydropyranone.
- Edwards, Hannah J.,Goggins, Sean,Frost, Christopher G.
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p. 6153 - 6166
(2015/05/13)
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- Diastereoselective syntheses via Prins cyclization, crystal structures determination and theoretical studies of cis-2,6-diphenyl-4- hydroxytetrahydropyran and analogues
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We report in this article the diastereoselective syntheses of tetrahydropyranyl derivatives 1-5, its cis configurational ascertainment by spectroscopy and finally the crystal structures determination that unequivocally shows the 1-5 configurations and its
- Silva,Sabino,Martins,Vasconcellos
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p. 478 - 487
(2013/03/29)
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- Synthesis, characterisation and antimicrobial activities of novel 7,9-diphenyl-1,2,4-triaza-8-oxa-spiro[4.5]-decan-3-thiones
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Some new 7,9-diaryl-1,2,4-triaza-8-oxa-spiro [4.5]-decan-3-thiones has been synthesised and their antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi, and antifungal activity against Candida albicans, Rhizopus sp., Aspergillus flavus and Aspergillus niger were examined. Compounds 14 and 15 against E. coli and S. typhi showed marked antibacterial activity. Similarly, compounds 13 and 15 against Rhizopus sp. and 13 and 14 against A. flavus exerted significant antifungal activities. Springer Science+Business Media, LLC 2011.
- Kabilan, Senthamaraikannan,Umamatheswari, Seeman
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scheme or table
p. 542 - 548
(2012/04/17)
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- Carbonyl umpolung reactivity of enals: NHC-catalyzed synthesis of aldol products via epoxide ring opening
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A novel one-pot N-heterocyclic carbene catalyzed synthesis of aldol products and their application to a facile and highly cis-selective synthesis of tetrahydropyran-4-ones is reported. The protocol involves carbonyl umpolung reactivity of enals in which the carbonyl carbon attacks nucleophilically on electrophilic terminal epoxides, regioselectively, to afford aldol adducts in good to excellent yields. Georg Thieme Verlag Stuttgart - New York.
- Yadav, Lal Dhar S.,Singh, Santosh,Rai, Vijai K.
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experimental part
p. 240 - 246
(2010/04/02)
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- The one-pot, multi-component construction of highly substituted tetrahydropyran-4-ones using the Maitland-Japp reaction
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A one-pot, multi-component reaction for the synthesis of highly substituted tetrahydropyran-4-ones, based on the long forgotten Maitland-Japp reaction has been realised. Two different aldehydes and a derivative of a β-ketoester can be condensed regioselectively in the presence of a Lewis acid to form tetrahydropyran-4-ones in excellent yields. The diastereoselectively of the reaction was found to be dependant upon the nature of the Lewis acid and the temperature at which the reaction was carried out. This procedure was also extended to the formation of tetrahydropyran-4-ones in greater than 95% enantiomeric excess. The Royal Society of Chemistry 2005.
- Clarke, Paul A.,Martin, William H. C.,Hargreaves, Jason M.,Wilson, Claire,Biake, Alexander J.
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p. 3551 - 3563
(2007/10/03)
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- Conformational effects upon the oxidation of some substituted oxan-4-ols
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Kinetics of oxidation of some epimeric pairs of oxan-4-ols by pyridinium fluorochromate (PFC) in the presence of sulphuric acid in aqueous acetic acid at 60°C have been investigated. The rate of oxidation is first order with respect to both the oxidant and the substrate concentrations at constant [acid]. The effect of solvent polarity on the reaction rates has also been studied. The order with respect to [H3O+] is found to be fractional at constant ionic strength in sulphuric acid. A suitable mechanism and the corresponding rate equation have been proposed. The reactivities of oxan-4-ols are rationalized on the basis of their conformational features. A twist conformation is assigned to t-2,t-6-diphenyl-c-3,c-5-dimethyloxan-r-4-ol and c-2,c-6-diphenyl-t-3,t-5-dimethyloxan-r-4-ol based on their oxidation rate constants.
- Mangalam,Gurumurthy,Arul,Karthikeyan
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p. 413 - 417
(2007/10/03)
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- Kinetics of oxidation of heterocyclic secondary alcohols by N-chloro-r-2,c-6-diphenyl-t-3 methyl piperidin-4-one (NCP) in perchloric acid medium
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An investigation of the kinetics of oxidation of epimeric piperidin-4-ols, oxan-4-ols, and cyclohexanol by N-chloro-r-2, c-6-diphenyl-t-3-methylpiperidin-4-one (NCP) in aqueous acetic acid in the presence of perchloric acid shows that the reaction is first-order each in substrate and oxidant. Both H3O+ and Cl- which catalyze the reaction, exhibit a fractional order kinetics. While increase in ionic strength increases the rate slightly, an inverse dependence is observed between rate and solvent polarity. Addition of r-2-c-6-diphenyl-t-3-methylpiperidin-4-one, one of the reaction products, did not influence the rate. Also, no kinetic isotope effect has been observed. A plausible mechanism consistent with these observations is proposed and the relative reactivities of the substrates are explained on conformational grounds.
- Selvaraj,Venkateswaran,Ramarajan
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p. 847 - 855
(2007/10/03)
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- Kinetics and mechanism of oxidation of 4-aminooxanes by chromium(VI)
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Kinetics of oxidation of variously substituted epimeric pairs of 4-aminooxanes by chromium(VI) have been investigated in aqueous acetic acid in the presence of sulphuric acid.The results indicate that the oxidation is first order in and fractional order in .The reaction is acid catalysed and susceptible to solvent polarity.A mechanism involving the formation of an intermediate followed by abstraction of α-hydrogen in the rate limiting step is proposed.The reactivity of aminooxanes has been discussed on the basis of conformational and electronic effects.Activation parameters have also been determined.
- Selvaraj, Kuppusamy,Hepsibha, E. Mary,Ramarajan, Krishnasamy,Chandrasekara, Nallappan
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p. 1052 - 1055
(2007/10/02)
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- Reactivity of Some Epimeric 4-Aminooxanes towards Oxidation by Cerium(IV)
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Kinetics of oxidation of four epimeric pairs of 4-aminooxanes by Ce(IV) in aqueous acetic acid in the presence of nitric acid, have been investigated.The oxidation is first order in .No definite order exists with respect to .A mechanism involving the abstraction of a H-atom from the α-C-H by Ce(IV) in the rate-limiting step is proposed.Equatorial amines react faster than axial amines.Added H(+) or NO3(-) increase the rate of oxidation.Rate is lowered by increase in the polarity of the medium.The conformational (steric) and electronic effects on the rate of oxidation are discussed.
- Chandrasekara, Nallappan,Ramarajan, Krishnasamy,Suja, Mathen,Selvaraj, Kuppusamy
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p. 471 - 474
(2007/10/02)
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- Dissociation Constants of Cyanohydrins of Some Tetrahydropyran-4-ones
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The dissociation constants of cyanohydrins of some substituted tetrahydropyran-4-ones have been determined at 30 deg in 80percent dioxane-water (v/v).The results substantiate the steric environment of the carbonyl group in these ketones.
- Baliah, V.,Mangalam, G.
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p. 947 - 948
(2007/10/02)
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- Oxidation of Substituted 1-Hetera-4-cyclohexanols by N-Bromsuccinimide
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The rates of NBS oxidation of some substituted 1-hetera-4-cyclohexanols have been measured at 50 deg in 80percent acetic acid-20percent water (v/v).The primary kinetic isotope effect is suggestive of the involvement of C-H or C-D bond of the hydroxy beari
- Jambulingam, M.,Nanjappan, P.,Natarajan, K.,Ramalingam, K.
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p. 390 - 394
(2007/10/02)
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- Steric Effects in the Oxidation of Oxan-4-ols and Thian-4-ols by Vanadium(V)
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The rates of oxidation of 20 heterocyclic alcohols by vanadium(V) have been measured at 60 deg C in aqueous acetic acid medium in the presence of sulfuric and perchloric acid.The data indicate an overall second-order reaction at constant acid concentration, first-order each in alcohol and oxidant.The conformational effects on the rates of oxidation of various heterocyclic alcohols are discussed.An interesting observation in the present study is that t-2,t-6-diphenyl-c-3,c-5-dimethyloxolan-r-4-ol, an axial alcohol, reacts slower than corresponding equatorial epimer, c-2,c-6-diphenyl-t-3,t-5-dimethyl-oxan-r-4-ol, which is contrary to general expectations.
- Arjunan, Periaswamy Gounder,Lakshmanan, Joghee Gowder,Chandrasekara, Nallappan,Ramalingam, Kondareddiar,Selvaraj, Kuppusamy
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p. 1183 - 1186
(2007/10/02)
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- Conformation and Reactivity of Some Substituted Oxan-4-ols in the Oxidation with Cerium(IV)
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The kinetics of the oxidation of some substituted oxan-4-ols by cerium(IV) in an aqueous acetic acid medium at 60 deg C in the presence of sulphuric acid have been investigated.The reaction is first-order each in oxidant and substrate at constant acid concentration. t-2,t-6-Diphenyl-c-3,c-5-dimethyloxan-r-4-ol, an axial alcohol, reacts slower than the corresponding equatorial epimer, c-2,c-6-diphenyl-t-3,t-5-dimethyloxan-r-4-ol.This anomalous observation and the reactivity of other oxanols towards oxidation have been discussed on the basis of conformational differences.
- Sureshkumar, Shanmugham,Chandrasekara, Nallappan,Ramalingam, Kondareddiar,Selvaraj, Kuppusamy
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p. 311 - 314
(2007/10/02)
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- Kinetics and Mechanism of the Oxidation of Some Heterocyclic Secondary Alcohols by N-Bromoacetamide in Acid Medium
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The kinetics of oxidation of 12 epimeric pairs of 1-hetera-2,6-diphenylcyclohexan-4-ols by N-bromoacetamide in the presence of perchloric acid in aqueous acid have been investigated.The oxidation is first-order in both oxidant and substrate and of minus-one-order in acetamide (an intermediate in the reaction) at constant acid concentration.The order with respect to H3O+ is observed to be unity at constant ionic strength in perchloric acid.Based on the observed deuterium kinetic isotope effect in the case of the epimeric pairs, 2,6-diphenyl-3,N-dimethylpiperidin-4-ols and 2,6-diphenyl-3-ethyl-N-methylpiperidin-4-ols, a mechanism involving the participation of an O-H bond in the rate-limiting step is proposed.The reactivities of various 1-heteracyclohexan-4-ols towards oxidation have been rationalised on the basis of conformational differences.The effect of solvent polarity on the rate has been studied.Activation parameters have also been evaluated.
- Jambulingam, Marimuthu,Napjappan, Palaniappan,Natarajan, Kumarasamy,Nagalingam, Jpgiah,Palaniswamy, Maran,et al.
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p. 1699 - 1702
(2007/10/02)
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