- A Convenient Synthesis of 8-Substituted Indolizines as Precursors to 5-Substituted Cycl{3.2.2}azine Derivatives
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The synthesis of 8-substituted indolizines is described via a two step process in which a 1,4-diketone, containing a tert-butyl group, is cyclocondensed with a trialkylsilyl protected pyrrole to provide 5,8-disubstituted indolizines in higher yields than the identical reaction with unprotected pyrrole. Cleavage of the tertbutyl group from the indolizine 5-position, by treatment with 85% phosphoric acid, provides 8-substituted indolizines in good yields. Treatment of 8-substituted indolizines with dimethyl acetylenedicarboxylate, in the presence of palladium-on-carbon, provides novel 5-substituted cycl{3.2.2} derivatives.
- Smith, Jonathan O.,Mandal, Braja K.
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p. 1441 - 1446
(2007/10/03)
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- Structure of Silylated Sulfonamides; a Silicon-29 Nuclear Magnetic Resonance Investigation
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The structures of eighteen silylsulfonamides have been determined by 29Si n.m.r.The chemical shifts of the compounds were compared with those of model compounds.The N-silyl tautomer was the only isomer observed, except in cases where strongly electron-withdrawing groups (e.g.Cl, NMe2) were attached to nitrogen; in such cases the O-silyl tautomer dominates.The results have been rationalised in terms of the effect of substituents on the S-N ?-bond order.An estimate of the hitherto unmeasured S=N molar bond enthalpy as 325 kJ mol-1 was obtained.
- Iley, Jim,Bassindale, Alan R.,Patel, Pravin
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