The ability of triplet nitrenes to abstract hydrogen atoms

Abstract

The enthalpies for H‐atom abstraction reactions by triplet imidogen as well as ethyl, alkoxycarbonyl, acyl, phenyl, and vinyl nitrenes were calculated using density functional theory calculations. These calculations show that H‐atom abstraction reactions are only feasible for triplet imidogen, alkoxycarbonyl, and acyl nitrenes in solution. The calculated charges on the N‐atoms (QNPA) in the nitrene correlate with the magnitude of the transition state barrier for the H‐atom abstraction reactions from methanol as a model reactant. Electron‐withdrawing substituents on these nitrenes make them less stable but do not affect the transition state barrier significantly. Thus, as the electron deficiency of the N‐atom in the nitrenes is increased, the H‐atom abstraction reaction becomes more feasible. Copyright © 2010 John Wiley & Sons, Ltd.

Computational study of singlet and triplet sulfonylnitrenes insertion into the C―C or C―H bonds of ethylene

“…Such a large difference allows to suggest that, apparently, N‐vinyltriflamide 3 is not formed in solution because much more favorable route for the system 3 (TfN)–ethylene is С‐addition leading to N‐triflylaziridine 1 from 1 ( 5′ ) or to N‐ethylidenetriflamide 2 from 1 ( 5 ). The increase of polarity of the solvent slightly decreases the barrier, but in the case of methanol side‐products from the reaction of TfN with methanol similar to those observed experimentally in the reaction with other sulfonylnitrenes may appear …”

“…Recently, the ability of triplet nitrenes to abstract hydrogen atom from the C―H bond of methanol as well as the dependence of the transition state barrier on the substituents at nitrogen were analyzed theoretically. The conclusion was made that as the electron deficiency of the nitrogen atom in the nitrenes is increased, the H‐atom abstraction becomes more feasible . This must favor the reaction of H‐abstraction for such electron‐deficient nitrenes as sulfonylnitrenes, especially those with strong electron‐withdrawing groups, like CF 3 .…”

“…The conclusion was made that as the electron deficiency of the nitrogen atom in the nitrenes is increased, the H-atom abstraction becomes more feasible. [44] This must favor the reaction of H-abstraction for such electron-deficient nitrenes as sulfonylnitrenes, especially those with strong electron-withdrawing groups, like CF 3 . As was mentioned above, the abstraction of olefin hydrogen atoms is a rare type of reaction with only two known examples, [14,15] but in our opinion this is mainly because in most of the studied systems other, more favorable, alternatives were available, such as insertion into the saturated C-H bonds in alkanes, substituted alkenes, alkylaromatics or aromatics.…”

“…The increase of polarity of the solvent slightly decreases the barrier, but in the case of methanol side-products from the reaction of TfN with methanol similar to those observed experimentally in the reaction with other sulfonylnitrenes may appear. [44] Addition of singlet trifluromethanesulfonylnitrene 1 (RSO 2 N) + C 2 H 4 0.0 0.0 0.0 N-Triflylaziridine 1 À89.8 À90.0 À90.6 TS 1-2 À30.1 À37.6 À43.4 N-Ethylidenetriflamide 2 À111.1 À112.2 À113.4 TS 2-4 À37.5 À42.4 À47.9 2-Trifluoromethyl-4,5-dihydro-1,2,3-oxathiazole 2-oxide 4 À82.4 À83.0 À83.7…”

Two‐step Two‐intermediate Photorelease Bolm‐McCulla Reaction: Dual Release of Nitrene and Atomic Oxygen Reactive Intermediates

“…The system is novel in that the compound incorporates photocleavable S-N and S-O bonds for a tandem process. Other work has been published on nitrenes, carbenes and atomic O from photolysis of sulfilimines, sulfoxides, pyridine N-oxide and related compounds (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25), but by nature are one-step processes. Relatedly, simultaneous formation of reactive intermediates has also been reported.…”