Intramolecular diyl trapping reactions. Arrhenius activation parameters for extrusion of nitrogen; Rate acceleration when diyl and diylophile are linked directly to one another

Diyl Trapping and Electroreductive Cyclization Reactions

“…For example, the Arrhenius activation energy for nitrogen loss from 63 , the diazene used in the asymmetric induction study described above, is 27.0 kcal/mol, and that for the dimethyl diazene 7 is 28.8 kcal/mol. In contrast, it is only 25.6 kcal/mol for both 79a and 80 . ,

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“…A concerted process would have afforded a single diene, 83 . In fact, a 1/1 mixture of dienes 83 and 84 was obtained, thereby implicating the existence of an intermediate, most likely the time-average planar, nitrogen-free diyl, 82 …”

“…37,38 One of the first examples to illustrate the chemistry of these systems involved the conversion of diazene 79a to the bicyclic diene 81 (R ) H), upon heating the former to reflux in acetonitrile. 37,38 In principle, this transformation could have occurred via a concerted eight-electron process, or through the intermediacy of a TMM diyl, 82. To differentiate between these possibilities, the deuterated diazene 79b was synthesized and studied.…”

“…In fact, a 1/1 mixture of dienes 83 and 84 was obtained, thereby implicating the existence of an intermediate, most likely the time-average planar, nitrogen-free diyl, 82. 37 Reasonably facile access to bicyclic furans is provided using this methodology, simply by heating the diazene to reflux in the solvent of choice. For example, enones 85 and 86 are converted to furans 87 and 88 in 87% and 70% yield, respectively.…”

A New Synthesis of Diazenes (Azoalkanes) Using 4-(S,S-Dimethylsulfoximino)- 1,2,4-triazoline-3,5-dione. The Construction of Diazenes from Amino Nitrenes via Base-Induced Sulfoximine Cleavage

“…This factor can prove advantageous in the synthesis of thermally labile diazenes. For example, while the diphenyl diazene 11c has an estimated half-life of roughly 2 min at 75 °C in acetonitrile, 2d, it can be isolated in a 77% yield after treatment of urazole 10c with aqueous potassium carbonate at that temperature for 5 h.…”