- Samarium(II) iodide-induced tandem reductive coupling-Dieckmann condensation reaction: One-step synthesis of bicyclic oxacyclopentanecarboxylate from bis-α,β-unsaturated esters
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The tandem cyclization of bis-α,β-unsaturated esters with SmI2-Sm-THF in the presence of catalytic amount of methanol was found to stereoselectively provide bicyclo[4.3.0]nonan-8-ones and bicyclo[3.3.0]octan-3-ones.
- Shinohara, Ikuo,Okue, Masayuki,Yamada, Yasuji,Nagaoka, Hiroto
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- Hydroxylated HMPA enhances both reduction potential and proton donation in SmI2 reactions
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HMPA is known to increase the reduction potential of SmI2. However, in many cases, the transferred electron returns from the radical anion of the substrate back to the Sm3+. This could be avoided by an efficient trapping of the radical anion: e.g., by protonation. However, bimolecular protonation by a proton donor from the bulk may be too slow to compete with the back electron transfer process. An efficient unimolecular protonation could be achieved by using a proton donor which complexes to SmI2, in which case the proton is unimolecularly transferred within the ion pair. A derivative of HMPA in which one of the methyl groups was substituted by a CH2CH2OH unit was synthesized. Cyclic voltammetry studies have shown that it resembles HMPA in its ability to enhance the reduction potential of SmI2, and reactivity studies show that it has also efficient proton shift capabilities. The various aspects of this additive were examined in the reactions of SmI2 with three substrates: benzyl chloride, methyl cinnamate, and anthracene.
- Halder, Sandipan,Hoz, Shmaryahu
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p. 2682 - 2687
(2014/04/17)
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- Stereoselective hydrocoupling of cinnamic acid esters by electroreduction: Application to asymmetric synthesis of hydrodimers
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The electroreduction of Ar-substituted methyl cinnamates in acetonitrile gave all-trans cyclized hydrodimers stereoselectively (58-90% de). In all cases, small amounts (2-symmetric dl-3,4-diaryladipic acids and trans-3,4-diarylcyclopentanones. The chiral auxiliary [(1R)-exo]-3-exo-(diphenylmethyl)borneol, prepared from (1R)-(+)-camphor, was highly effective for the stereoselective hydrocoupling of its cinnamates by electroreduction. From the resulting hydrodimers, (3R,4R)-3,4-diaryladipic acid esters and (3R,4R)-3,4-diarylhexane-1,6-diols were synthesized in 87-95% ee.
- Kise, Naoki,Iitaka, Shumei,Iwasaki, Keisuke,Ueda, Nasuo
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p. 8305 - 8315
(2007/10/03)
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- The effect of electrochemically formed aluminum salts on the electrochemical cyclisation of methyl cinnamate
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Electrochemical cyclisation of methyl cinnamate with dielectrophiles has been improved by the presence of an aluminum salt which was pre-formed in situ by the electrolysis of a carboxylic acid with a sacrificial aluminum anode. High yields of three, five and six-membered cyclic products have been obtained in the reactions of methyl cinnamate with dichloromethane, 1,3- dibromopropane, and 1,4-dibromobutane.
- Guellue, Mustafa
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p. 3225 - 3228
(2007/10/03)
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