Substituent‐Dependent Competition between 1,5‐ and 3,5‐Cyclization in Vinly Azides; 4H‐Triazoles from 3,3‐Diazido‐2‐cyanoacrylic Acid Methyl Ester and Primary Amines

Synthesis and Chemistry of Organic Geminal Di- and Triazides

“…While the photochemical decomposition was not examined in further detail, the thermal reaction of geminal vinyl diazides is well-studied (Scheme 17) [95,96,97,98,103,104,105,106,107,108]. The key intermediate is the very electrophilic [109] double acceptor-substituted N -cyanoimine 86 .…”

“…The existence of this intermediate 86 was also proven by cycloaddition with 2,3-dimethylbuta-1,3-diene leading to the Diels-Alder product 87 [95,96,97,108,109]. In the presence of alcohols [95,96,108,109] or amines [104,105,106,107,108], the N -cyanoimine 86 is immediately attacked at the electrophilic carbon and, after elimination of hydrogen cyanide, isolable structures 88 and 89 are obtained in good yields. Reaction of the N -cyanoimine 86 with hydrazines leads to 90 in an analogous fashion.…”

“…Formally, this must be seen as a 1,4-addition followed by elimination of hydrazoic acid. The resulting vinyl azides 92 can, in most cases, be isolated in good yields as crystalline solids [98,102,104,105,106,107,108,110,111]. Because of the thermal instability of geminal vinyl azides 83 , this reaction has to be performed at temperatures below −20 °C.…”

“…Otherwise, the N -cyanoimine 86 (Scheme 17) would be generated before an intermolecular reaction can take place. As nucleophiles, primary [98,102,104,105,107,108,110,111] and secondary [102,107,111] amines, diamines [106,108,111] and hydrazines [98] were tested. With diamines, the substitution occurs either on two different molecules of the diazide 73 generating vinyl azides 93 [106,108,111] or on the same molecule delivering cyclic products 94 [106].…”