Ketenaminals as 1,3-dinucleophiles in the synthesis of condensed 1,4-diazines and 1,2,4-triazines

Acetyl ketene aminals in Nenitzescu reaction

“…3-Acetyl-2-amino-7a-hydroxy-I-phenyl-5,7a-dihydro-I Hindol-5-one (4). A solution of benzoquinone (3) 2-Aeetyl-I-amino-1-benzoylamino-2-(2,5-dihydroxyphenyt)ethene (7).…”

Use of tandem AN-AN reactions for the synthesis of thiazolo[4,5-e]-1,2,4-triazines

“…Several examples of the tandem A N -A N reactions between 1,2,4-triazinium salts and bifunctional nucleophiles have been reported; [3][4][5][8][9][10] however, the patterns of heterocyclic fragments annelated to the 1,2,4-triazine ring are rather limited. Due to the relatively low stability of tetrahydrotriazines, only two types of condensed systems, i.e., pyrrolo[2,3-e]-and furo[2,3-e]-1,2,4triazines, have so far been obtained by the reactions of 1,2,4triazinium salts with acetoacetamides, 3,8,9 ketene-N,N'-aminals, 10 and other C,N-or C,O-dinucleophiles.…”

“…Several examples of the tandem A N -A N reactions between 1,2,4-triazinium salts and bifunctional nucleophiles have been reported; [3][4][5][8][9][10] however, the patterns of heterocyclic fragments annelated to the 1,2,4-triazine ring are rather limited. Due to the relatively low stability of tetrahydrotriazines, only two types of condensed systems, i.e., pyrrolo[2,3-e]-and furo[2,3-e]-1,2,4triazines, have so far been obtained by the reactions of 1,2,4triazinium salts with acetoacetamides, 3,8,9 ketene-N,N'-aminals, 10 and other C,N-or C,O-dinucleophiles. 5 It should be noted that all ring systems hitherto annelated in this way to 5,6-unsubstituted 1,2,4-triazines are heterocycles bearing one heteroatom, so that at least one of the two newly formed bonds in the fused tetrahydrotriazine systems is a C-C bond, enhancing the stability of the adducts.…”