130460-41-2Relevant academic research and scientific papers
A Convenient Synthesis of 8-Substituted Indolizines as Precursors to 5-Substituted Cycl{3.2.2}azine Derivatives
Smith, Jonathan O.,Mandal, Braja K.
, p. 1441 - 1446 (1997)
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.
THE SYNTHESIS AND CHEMISTRY OF AZOLENINES. PART 18. PREPARATION OF 3-ETHOXYCARBONYL-3H-PYRROLES VIA THE PAAL-KNORR REACTION, AND SIGMATROPIC REARRANGEMENTS INVOLVING COMPETITIVE ESTER MIGRATIONS TO C-2, C-4 AND N.
Chiu, Pak-Han,Sammes, Michael P.
, p. 3439 - 3456 (2007/10/02)
3H-Pyrrole-3-carboxylic esters (4) have been prepared, in some cases together with isomers (5) and (6) having exocyclic double bonds, by cyclization of suitably substituted 2-ethoxycarbonyl-1,4-diketones (1) with liquid ammonia, followed by dehydration of the isolable 2-hydroxy-3,4-dihydro-2H-pyrrole intermediates (2) and (3) with aluminia in boiling solvents.Prolonged heating in toluene or p-xylene converts the 3H-pyrroles (4) quantitatively into isomeric 4-esters (11) and N-esters (13) of 1H-pyrroles via competitive sigmatropic rearrangements.Isolable intermediate 2H-pyrrole-2-carboxylic esters (12) are converted similarly into the same products, under the same conditions.Detection of 3H-pyrroles (4) as intermediates in the latter reaction demonstrates for the first time the reversibility of the thermal 2H-pyrrole to 3H-pyrrole interconversion.
