- A mild, catalytic and efficient Nazarov cyclization mediated by phosphomolybdic acid
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A mild, selective and efficient Nazarov cyclization of divinyl ketones catalyzed by phosphomolybdic acid (PMA) is described. The process demonstrates a broad substrate scope with functional group tolerance under short reaction times. PMA supported on silica gel is more efficient than the bulk catalyst and is recycled up to three times without significant activity loss.
- Murugan, Kaliyappan,Srimurugan, Sankareswaran,Chen, Chinpiao
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supporting information; experimental part
p. 1127 - 1129
(2010/06/18)
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- The Use of Diazophosphonates in the Synthesis of Cyclic Ethers
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Two routes to cyclic ethers based on diazophosphonates are described.The first involves the rhodium(II) catalysed O-H insertion of 2-propanol followed by Wadsworth-Emmons reaction to give the enol ethers 3, and deprotection and cyclisation to the cyclic enol ethers 5.The second route involves the preparation of aldehyde and ketone phosphonates 9, also by rhodium carbenoid O-H insertion reactions, followed by functional group interconversion.On treatment with sodium hydride the phosphonates 9 undergo intramolecular Wadsworth-Emmons reaction to give cyclic ethers 13. Key Words: diazophosphonate; rhodium carbenoid; Wadsworth-Emmons; cyclic ether
- Moody, Christopher J.,Sie, Eric-Robert H. B.,Kulagowski, Janusz J.
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p. 3991 - 4004
(2007/10/02)
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- Diazophosphonates in Cyclic Ether Synthesis. Use of the Intramolecular Wadsworth-Emmons Reaction
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Treatment of the phosphonates 3, derived from the diazophosphonates 1 and 2 by rhodium carbenoid O-H insertion reactions, with sodium hydride in THF results in intramolecular Wadsworth-Emmons reaction and formation of the cyclic ethers 4. Key words: Diazophosphonate; rhodium carbenoid; Wadsworth-Emmons; cyclic ether
- Moody, Christopher J.,Sie, Eric-Robert H. B.,Kulagowski, Janusz J.
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p. 6947 - 6948
(2007/10/02)
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- SYNTHESIS OF DIASTEREOISOMERIC 2,4,7-TRIOXA-3-PHOSPHA-3-R-3-THIONOBICYCLO(4.4.0) DECANES AS A MODEL FOR PHOSPHORUS NUCLEOPHILIC SUBSTITUTION STUDIES.
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2,4,7-Trioxa-3-chloro, 3-fluoro, 3-dimethylamino, 3-methoxy, 3-(2-propanoxy)-3-phospha-3-thionobicyclo (4.4.0) decanes (trans fusion) have been prepared.The precursor diol, 2-hydroxymethyl-3-hydroxytetrahydropyran (2R*, 3S*), was obtained in two steps from 3,4-dihydro-2H-pyran.The chloridates 7a and 7b were separated by high performance liquid chromatography and the stereochemistry of the nucleophilic substitution at phosphorus (with fluoride anion, dimethylamine, methanol, 2-propanol) for each isomer was studied.The substitution of chlorine was found to occur mostly with inversion of configuration for the two isomers.Equilibrium constants were measured for 7a7b and 9a9b making it possible to calculate the corresponding standard free energies.A kinetic study of the 2-propanolysis of 7a and 7b showed that 7b reacted more slowly than 7a.It was found that the difference between the free energy of activation (ΔΔG (b-a)=1 Kcal/mol for the two isomers is close to the calculated value of the standard free energy variation ΔG0 (b-a)=-1.3 Kcal/mol.The difference between the observed reaction rates is probably due to the relative thermodynamic stabilities of the reactants.
- Bouchu, D.,Dreux, J.
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