The reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethy1)-1, 3-0xazol-S (2H)- ones 5 in MeCN or THF at 5G8Oo leads to S-(dimethylamino)-3, 6-dihydropyrazin-2 (lH)- ones 6 (Scheme 3). Reactionmechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH-acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via ...
