Indolizine reaction with diethyl acetylenedicarboxylate

Despite its 10-electron aromatic 7t-system, indolizine apparently participates as an 8-electron system in its reaction with diethyl acetylenedicarboxylate, though the process may be stepwise and not concerted. By carrying out the reaction in the presence of a noble metal as catalyst, the initial adduct is converted into an aromatic cyclazine (28.5)."... 

The reaction of indolizines with dialkyl acetylenedicarboxylates in the presence of a dehydrogenating catalyst leads to 1,2-dicarbalkoxycycl-[3,2,2]azines.22 23 Methyl phenylpropiolate may be used instead, although attempts to effect reaction between indolizine and certain other dienophiles including diphenylacetylene, diethyl azodicarboxylate, and 1,3-cyclohexadiene were unsuccessful. Hydrolysis of the diesters yielded the corresponding acids. Subsequent decarboxylation proceeded in high yield using copper chromite in quinoline [Eq. (5)]. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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