- Facile synthesis of Z -alkenes via uphill catalysis
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Catalytic access to thermodynamically less stable Z-alkenes has recently received considerable attention. These approaches have relied upon kinetic control of the reaction to arrive at the thermodynamically less stable geometrical isomer. Herein, we present an orthogonal approach which proceeds via photochemically catalyzed isomerization of the thermodynamic E-alkene to the less stable Z-isomer which occurs via a photochemical pumping mechanism. We consider two potential mechanisms. Importantly, the reaction conditions are mild, tolerant, and operationally simple and will be easily implemented.
- Singh, Kamaljeet,Staig, Shannon J.,Weaver, Jimmie D.
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supporting information
p. 5275 - 5278
(2014/05/06)
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- Convergent synthesis of conjugated 1,2-disubstituted E-allylic alcohols from two aldehydes and methylenetriphenylphosphorane
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β-Lithiooxyphosphonium ylides, made in situ from an aldehyde and methylenetriphenylphosphorane, react with a second aldehyde to form E-allylic alcohols. α-Branching and α,β-unsaturation in the second aldehyde, together with the lack of further substitution on the phosphorane carbon play important roles in selectivity. A range of these aldehydes, in addition to aromatic aldehydes as the second aldehyde also provided synthetically useful access to E-allylic alcohols.
- Hodgson, David M.,Persaud, Rosanne S. D.
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supporting information
p. 7949 - 7951
(2013/06/27)
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- Microwave-assisted minutes synthesis of bioactive phenylbutanoids occurring in Zingiber cassumunar
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Microwave-assisted condensation of benzaldehyde (3a,b) with acetone in aqueous sodium hydroxide adsorbed on basic alumina provides phenylbutenone (4a-4b) in 68-71% yield within 4 min, which upon further reduction with sodium borohydride and basic alumina gives phenylbutenol (5a,b) in 91-94% yield within 2 min. Dehydration of 5 with anhydrous copper (II) sulfate gives phenylbutadiene (1a,b), a metabolite of Zingiber cassumunar, within 3 min in 42-48% yield, respectively. All the steps involve environmental friendly solvents and reagents, mild reaction conditions, and overall formation of product 1a,b from 3a,b in 34-38% yield within 9 min under microwave irradiation. 2005 Springer Science+Business Media, Inc.
- Joshi,Singh,Sharma,Sinha
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p. 370 - 373
(2007/10/03)
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- PHENYLBUTENOID DIMERS FROM THE RHIZOMES OF ZINGIBER CASSUMUNAR
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Two new phenylbutenoid dimers, (+/-)-trans-3-(2,4,5-trimethoxyphenyl)-4-cyclohexene and cis-1,2-biscyclobutane, have been isolated from the fresh rhizomes of Zingiber cassumunar along with the two known phenylbutenoid dimers.Their structures were elucidated by spectroscopic and chemical methods.The stereochemistry of these cyclohexene compounds was clarified on the basis of 1H NMR data of their derivatives.The substituted positions for the 3,4-dimethoxystyryl groups of the cyclobutane compound were confirmed from a Cope rearrangement product in the pyrolysis of the cyclobutane, and the stereochemistry of the cyclobutane was confirmed by 1H NMR evidence.Key Word Index - Zingiber cassumunar; Zingiberaceae; rhizomes; phenylbutenoid; dimer.
- Jitoe, Akiko,Masuda, Toshiya,Nakatani, Nobuji
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p. 357 - 364
(2007/10/02)
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