Communications: The Formation of Nitrile Imines in the Thermal Breakdown of 2,5-Disubstituted Tetrazoles

Oxadiazoles

“…Furthermore, the use of C,N-Diphenyl nitrilimine 728 reacts, by 1,3-dipolar cycloaddition, with aldehydes 754 to produce in 50-75% yield 5-aryl-substituted-2,4-diphenyl-1,3,4-oxadiazolines (755) (Scheme 13.239) [555,556]. N-Substituted 2,3-dihydrooxadiazoles have been prepared recently by intramolecular cyclization of protected amino-aldehydes (1,5-dipolar cycloaddition) [557].…”

Synthesis of Novel Tetrahydro-1<i>H</i>-pyrazolo[4,3-<i>c</i>]pyridines <i>via</i> Intramolecular Nitrilimine Cycloaddition

“…Intramolecular 1,3-dipolar cycloaddition of nitrilimines with alkynes is a well documented method for the preparation of fused polycyclic pyrazoles. 10,11) While nitrilimines have been obtained by a number of means including the thermolysis of 2,5-disubstituted tetrazoles 12) or 1,3,4-oxadiazolin-5-ones, 13) the photolysis of sydnones, 14) and the oxidation of aldehyde hydrazones, 15) they are most conveniently derived from the reaction of hydrazonoyl chlorides with base or silver salts. 16) This approach required the preparation of acyl hydrazide 16 as illustrated in Chart 3.…”

Tandem in situ generation and 1,5-electrocyclization of N-hetaryl nitrilimines. A facile methodology for synthesis of annulated 1,2,4-triazoles and their acyclo C-nucleosides

“…[23][24][25][26][27][28] The mechanism of this 1,3-elimination reaction has been studied. [26][27][28][29][30][31][32] Dehydrohalogenation reaction of the hydrazonyl halides can also be effected by silver nitrate. 28,33,34 5.…”