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À propos de : Synthesis of 2,5-Disubstituted Thienosultines and Their ThermalReactions with Dienophiles and Nucleophiles        

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  • Synthesis of 2,5-Disubstituted Thienosultines and Their ThermalReactions with Dienophiles and Nucleophiles
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  • The 2,5-disubstituted thienosultines (5,7-disubstituted 1,4-dihydro-1H-3λ4-thieno[3,4-d][2,3]oxathiin-3-oxides) 5a−d were prepared from the corresponding dichlorides 4a−d with the commerciallyavailable Rongalite (sodium formaldehyde sulfoxylate) in 17−60% yields. When heated in thepresence of electron-poor dienophiles, sultines 5a−d underwent elimination of SO2, and the resultingnon-Kekulé biradicals 7a−d were intercepted as the 1:1 adducts 8−12 in good to excellent yields.The pyrolysis of sultines and sulfolenes with different concentrations of dienophiles revealed thateither a preequilibrium between starting reagents and biradical species or Diels−Alder and retro-Diels−Alder reaction mechanisms may be involved; however, more work is necessary to establishthe proposed mechanisms. Reaction of sultine 5b with nBuLi was found to undergo a nucleophilicring-opening reaction to give sulfinyl alcohol 17 after H2O workup. When sultine 5a was heated inbenzene in a sealed tube in the presence of methanol, methanol-d4, or 2-mercaptoethanol, therespective 1:1 trapping adducts 19−21 as well as the rearranged sulfolene 6a were isolated insimilar amounts. The isolation of adducts 19−21 may be explained by the involvement of eitherbiradical or ionic intermediates during the pyrolysis.
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