Indolizines physical properties

Attempts to confirm the structure of 32 by conversion into the methyl indolizine and comparison with an authentic sample were inconclusive. However, rearrangement of 27 with acetic acid or phenol gave an indolizine triester formulated as 33 which could be converted into 34. This last product had markedly different physical properties from 32 and its decarboxylation product was identical with 3-methylindolizine [Eq. (9)]. 

In another example of oxidation without ring fission, the major product obtained from the reaction between methyl 2-pyridylacetate and ethyl-a-bromopropionate was not the expected indolizine 151, but a compound whose chemical and physical properties suggested the structure 152 (Scheme 20). When the reaction was repeated under... 

Quantum chemical calculations of indolizine and its aza derivatives have been reviewed (77HC(30)117). Attempts to correlate the results with various physical and chemical properties have not always been crowned with success. (A critical discussion of semi-empirical molecular orbital methods is given in Section 3.01.7.) A qualitative discussion using single structures may be appropriate. 

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