4-Azaazulenium salts

Finally, the pyrrolo[2,l-/ [l,2,4]triazine moiety was also encountered in azulene derivatives. Reactions of l,8-diamino-3-phenyl-l-azaazulenium salt 54 with triethyl orthoformate and acetic anhydride gave l-phenyl-2a,3,5-mjzjbenzb. //]jzulcncs 55 and 56. The reaction of the same salt with ethyl pymvate gave 4-acetyl-l-phenyl-2a,3,5-triazabenz[c, /]azulene 14 <2000H(53)323>. 

An important method of tropone O-alkylation consists of the use of trialkyloxonium tetrafluoborate (70JA6382). Thus, violet azaazulenium salt... 

The formation of azaazulenium or pyrrolotropylium salts by protonation of azaazulenes is exemplified by the acenaphtho-fused com-... 

The heterocyclic alkyl quaternary salts used for preparing spiropyrans are usually obtained by N-alkylating the heterocyclic bases by standard methods. The common bases having an active methyl group of the indolenine, benzothiazole, benzoxazole, and quinoline series some of their substitution products, and a few of their quaternary salts are commercially available. The pyrylium, thiopyrylium, 2-azaazulenium and bcnz[c,d]indolenium salts needed for potentially infrared-absorbing spiropyrans are not (as of the time of writing). 

Thus, the condensation of 2-phenyl-l,3,6-trimethyl-2-azaazulenium perchlorate with 5-nitrosalicylaldehyde gave the cationic styryl dye (A,max 510 nm) in 56% yield.139 This dye is the salt of the open form of the corresponding spiropyran, and upon treatment with base, a reaction which was not originally reported, was found to give the expected dye (126), which absorbs at 733 and 536 nm. This material did not thermally fade or photobleach to any significant extent with visible light in either polar or nonpolar solvents.7... 

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