- β-cyclodextrin immobilized onto dowex resin: A unique microvessel and heterogeneous catalyst in nucleophilic substitution reactions
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The catalytic activity of β-cyclodextrin immobilized on Dowex resin as an efficient solid-liquid phase transfer catalyst was developed for the synthesis of alkyl thiocyanates and phenacyl derivatives in water. The nucleophilic substitution reactions were performed under mild reaction condition and gave the products in excellent yields. Furthermore, the catalyst could be recycled by facile separation without any loss of activity.
- Kiasat, Ali Reza,Zarinderakht, Nasrollah,Sayyahi, Soheil
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- An ionic liquid supported on magnetite nanoparticles as an efficient heterogeneous catalyst for the synthesis of alkyl thiocyanates in water
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The present study describes a convenient method to synthesize alkyl thiocyanates from alkyl halides with the use of a novel nanomagnetic-supported organocatalyst (MNP@PEG-ImCl). The new supported ionic liquid is fully characterized by field-emission scanning electron microscopy (FESEM), Fourier-transform infrared (FT-IR), energy dispersive X-ray analysis (EDAX), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) as well as thermogravimetric analysis (TGA) techniques. It is noteworthy that we observed easy separation of the catalyst from the reaction mixture by a simple magnetic decantation and its reutilization many times without any appreciable loss of activities.
- Fallah-Mehrjardi, Mehdi,Sayyahi, Soheil
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- Synthetic scope, computational chemistry and mechanism of a base induced 5-endo cyclization of benzyl alkynyl sulfides
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We present an experimental and computational study of the reaction of aryl substituted benzyl 1-alkynyl sulfides with potassium alkoxide in acetonitrile, which produces 2-aryl 2,3-dihydrothiophenes in poor to good yields. The cyclization is most efficient with electron withdrawing groups on the aromatic ring. Evidence indicates there is rapid exchange of protons and tautomerism of the alkynyl unit prior to cyclization. Theoretical calculations were also conducted to help rationalize the base induced 5-endo cyclization of benzyl 1-propynyl sulfide (1a). The potential energy surface was calculated for the formation of 2,3-dihydrothiophene in a reaction of benzyl 1-propynyl sulfide (1a) with potassium methoxide. Geometries were optimized with CAM-B3LYP/6-311+G(d,p) in acetonitrile with the CPCM solvent model. It is significant that the benzyl propa-1,2-dien-1-yl sulfane (6) possessed a lower benzylic proton affinity than the benzyl prop-2-yn-1-yl sulfane (8) thus favoring the base induced reaction of the former. From benzyl(propa-1,2-dien-1- yl sulfane (6), 2,3-dihydrothiophene can be formed via a conjugate base that undergoes 5-endo-trig cyclization followed by a protonation step.
- Motto, John M.,Castillo, álvaro,Greer, Alexander,Montemayer, Laura K.,Sheepwash, Erin E.,Schwan, Adrian L.
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p. 1002 - 1010
(2011/03/19)
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