RING EXPANSIONS OF N-METHYL-1,2,5-OXADIAZOLIUM AND 1,2,3-TRIAZOLIUM PERCHLORATE SALTS WITH BASES TO 6-MEMBERED AZINES - DIRECT-DETECTION OFAN ADDITION INTERMEDIATE IN AN ADDITION-ELIMINATION MECHANISM AND A DEGRADATION OF 1,2,5-OXADIAZOLIUM SALTS TO ALPHA-CYANO NITRONES

Reactions of 2-methyl-1,2,5-oxodiazolium perchlorate salts and 1-methy l-2-aryl-1,2,3-triazolium perchlorate salts with the bases KCN, NaOEt, KOBut, LiNPr2i, give ring expansions to substituted 1,2,5-oxadiazines and 1,2,4-triazines. With cyanide as base the reactions follow an add ition-elimination pathway and in two cases the addition intermediate h as been isolated or directly detected by low-temperature NMR spectrosc opy. The oxadiazolium system with cyanide also gives a useful new rout e to alpha-cyano nitrones via a ring degradation which competes with r ing expansion. The reactions with KOBut and LiNPr2i do not involve an addition of the base to the azolium salt. Reactions have been monitore d by C-13 NMR spectroscopy by using (CN-)-C-13. An X-ray crystal struc ture is reported for (E)-N-(alpha-cyanobenzylidene)methylamine N-oxide .