- Synthesis and Reactions of α-Chloro-β,γ-unsaturated Esters. 1
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Four new α-chloro-β,γ-unsaturated esters were prepared in good yield by the reaction of hypochlorous acid with substituted ethyl 2-butenoates.Reaction of these substituted allylic chlorides with several nucleophiles has been investigated.Thiophenol in the presence of aqueous sodium hydroxide react with ethyl 2-chloro-3-methyl-3-butenoate (2) to give 6, whereas ethyl 2-chloro-2,3-dimethyl-3-butenoate (1) is unreactive.Tertiary allylic chlorides 1, 3 and 4 react with secondary amines to give exclusive abnormal SN2 reaction products.With benzylamine abnormal SN2 substitution is followed by cyclization to give 1-benzyl-3-pyrrolin-2-ones.While ethyl lithioacetate reacts with 1 to give acylation product 18, sodium diphenylmethide in liquid ammonia undergoes alkylation on the tertiary carbon possibly by an electron-transfer reaction pathway.Lithio-1,3-dithiane reacts with 1 to give 2,3-dimethyl-6,10-dithiaspirodec-2-en-1-one (20) via a two-step process, viz., acylation followed by anovel variation of the intramolecular abnormal SN2 reaction.Raney nickel desulfurization of 20 gave 2,3-dimethyl-2-cyclopenten-1-one.Synthetic and mechanistic implications of these results are discussed.
- Mathew, Jacob,Alink, Ben
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p. 3880 - 3886
(2007/10/02)
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- ELIMINATIVE DEOXYGENATION: A FACILE SYNTHESIS OF α-CYANO AND α-CARBOALKOXY SUBSTITUTED VINYL SULFIDES
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The facile eliminative deoxygenation of α-cyano and carboalkoxy sulfoxides by trimethylsilyl triflate under mildly basic conditions results in the formation of α-thiophenyl substituted α,β-unsaturated nitriles and esters in high yields.
- Miller, R. D.,Haessig, R.
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p. 2395 - 2398
(2007/10/02)
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- THE AdNSNE MECHANISM IN THE REACTION OF PHENOL AND BENZENETHIOL WITH α-BROMO MICHAEL ACCEPTORS IN THE K2CO3-ACETONE SYSTEM
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In the reaction of α-bromo Michael acceptors with either phenol or benzenethiol formal substitution of the vinylic bromine proceeds through addition of the phenolic reagent, followed by nucleophilic substitution and β-elimination (AdNSNE mechanism) in the system K2CO3-acetone.The process is shown to be stereospecific in the case of 2a,b and 3b,c, leading to the corresponding Z isomer.The reactivity of substrates 1-4 is discussed in terms of their structural features.
- Rosnati, Vittorio,Saba, Antonio,Salimbeni, Aldo,Vettori, Umberto
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p. 249 - 256
(2007/10/02)
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