The structure of 3,4-dihydropyrrolo[1,2-a]pyrazine and its N-protonate
d form is studied by ab initio calculations. Examples of the reactivit
y of this poorly studied system are presented in which it is shown tha
t the imino moiety does not react with dienes but does undergo inter-
and intramolecular 1,3-dipolar cycloadditions by reaction of azomethin
e ylides of this bicyclic system with suitable dipolarophiles. (C) 199
7 Elsevier Science Ltd.