THERMOLYSE COMPAREE D'ENAMINOESTERS CYCLIQUES A CINQ ET SIX CHAINONS : SYNTHESE DE TETRAHYDROINDOLES ET D'OXAZOLES
The thermal behaviour of cyclic enaminoesters 1a-d shows a divergence of chemioselectivity as a function of ring size : six and five ring derivatives lead respectively to tetrahydroindoles (3a,b and 4a,b) and oxazole (5c,d).These results may be rationalized by geometrical constraints during the electrocyclisation of intermediate azomethine ylides 5.