Tetrabromo-£-benzoquinone reacts with l-(cyclopentenyl) piperidine and l-(1-cyclohexenyl) piperidine to give the open (1:1) adduct (Ia,b) or (I'a,b), whereas it reacts with 4-(l-cyclopentenyl) morpholine to give the open (1: 1) addition product (I c or I' c) together with the cycl i c (1: 1) addition product (1Ia or Il'a). However, it reacts with 4-(l-cyclohexenyl) morpholine to give the cyclic (1:1) addition product (lib or II'b).


N G KANDILE ,T M A LATIF ,