Research on 1-aza two-ring systems

Mixtures of isomeric 5-, 6-, and 7-carbethoxymethyl-1,2-dihydropyrrolizines were obtained by reaction of 1,2-dihydropyrrolizines with ethyl diazoacetate. The effect of the position of the alkyl groups in the two-membered ring on the ratio of isomers in the reaction products is demonstrated. A method for the isolation of 5-carbethoxymethyl-1,2-dihydropyrrolizines from the mixtures of isomers based on the difference in their reactivities in diazo coupling is described. The preferred conformations of the two-membered rings in the 5-carbethoxymethyl-1,2-dihydropyrrolizines are judged from the PMR spectral data.