Synthesis of indolizines by intramolecular cyclisation of pyridinium allylides [1-(1-pyridinio)prop-2-enides]
- 1 January 1975
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 1
- No. 6,p. 575-579
- https://doi.org/10.1039/p19750000575
Abstract
Pyridinium ethoxycarbonyl-(3-oxocyclohexen-1-yl)methylides (VII)–(IX) and 3,3-diacyl-1-ethoxycarbonylallylides (X)–(XIII) are prepared by the reaction of 1-ethoxycarbonylmethylpyridinium bromides (III) and (IV) with 3-chlorocyclohex-2-enones and 3-ethoxymethylenepentane-2,4-dione or diethyl ethoxymethylenemalonate, respectively. Refluxing the ylides (VII)–(IX) in xylene affords the ethyl 10-oxo-7,8,9,10-tetrahydropyrido[2,1-a]isoindole-6-carboxylates (XVI)–(XVIII), and the ylides (X) and (XII) give diethyl indolizine-1,3-dicarboxylate (XIX) and ethyl 1-acetylindolizine-3-carboxylate (XX), respectively. However, similar treatment of the ylides (XI) and (XIII) affords ethyl indolizine-3-carboxylate (XXVII) and the keto-ester (XX), respectively. The mechanisms for the formation of the indolizine derivatives are discussed.Keywords
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