Thermal and photochemical additions of azo esters to unsaturated systems—II

Efficient C–H/C–N and C–H/C–CO–N Conversion via Decatungstate-Photoinduced Alkylation of Diisopropyl Azodicarboxylate

“…The photochemically induced addition of ethers (e.g., 1,4-dioxane) or alkenes (e.g., cycloheptene) onto an azodicarboxylate gave the corresponding substituted hydrazides in variable yields. In most of these reactions, however, the radical source was employed as the reaction medium, which poses problems in terms of efficiency in synthetic planning.…”

Oxime Radical Promoted Dioxygenation, Oxyamination, and Diamination of Alkenes: Synthesis of Isoxazolines and Cyclic Nitrones

“…To improve the yield, we turned our attention to dialkyl azodicarboxylates such as DEAD and DIAD (diisopropyl azodicarboxylate), which are known to react with NHPI (N-hydroxyphthalimide) and TEMPOH to afford the PINO (phthalimido-N-oxyl) radical and TEMPO, respectively. [13] Besides the importance of the isoxazoline structure motif, the formation of compounds 2 a and 3 a involves dioxygenation and oxyamination, respectively, of unactivated alkenes, and these are two types of reactions which are of synthetic significance. [12] To our delight, when DEAD (1 equiv) was used as the oxime radical initiator, and TEMPO (2 equiv) was used as the carbon radical trapping agent, the same product 2 a was obtained in 93 % yield along with a tiny amount of the DEAD-trapped by-product isoxazoline 3 a (Scheme 3, con-Scheme 1.…”

“…This result demonstrates clearly that DEAD could serve as an oxime radical initiator as well as carbon radical trapping agent in the reaction. [13] Besides the importance of the isoxazoline structure motif, the formation of compounds 2 a and 3 a involves dioxygenation and oxyamination, respectively, of unactivated alkenes, and these are two types of reactions which are of synthetic significance. [14] To examine the scope of the present protocols, a variety of b,g-unsaturated ketoximes were subjected to the reaction conditions as shown in Scheme 3.…”

Nitrogen-Centered Radical Scavengers

“…Evidence for this reaction type was initially reported by several groups: Alder et al, 55 Horner and Naumann, 56 Huisgen and Pohl 57 and Shah and George. 58 Results from a later study by Cadogan and co-workers 59 are shown in Scheme 34. Phenyl radicals 138, when generated from dibenzoyl peroxide (139), underwent addition to azo dicarboxylates 140.…”