The photolysis of sulfonyl azides in isopropyl alcohol

Abstract

Sulfonyl azides in isopropyl alcohol solution give the corresponding sulfonamides, acetone, and nitrogen either on direct irradiation of the azide or on selective irradiation of added benzophenone. Detailed studies with methanesulfonyl azide revealed high quantum yields and rates that showed complex dependences on the light intensity and on the concentrations of azide and benzophenone. A radical chain mechanism, evidently consisting of two propagation sequences, is involved. Chains appear to be terminated by radicals derived from isopropyl alcohol and from benzophenone. e wish to report our discovery and mechanistic W characterization of a photochemical reaction in which sulfonyl azides are reduced to sulfonamides by isopropyl alcohol solvent, according to eq 1. The OH 0 I II I RSOzNa + CHlCCHl + RSOzNHz + C H~C C H B + NP (1) H reaction occurs in the absence of oxygen (1) on direct irradiation of the azide, (2) on selective irradiation of benzophenone added as a sensitizer, (3) on thermal treatment of the solution at its reflux temperature (SO"), or (4) on addition of small amounts of ferrous chloride and hydrochloric acid to a solution of the azide in the alcohol.3 We optimized the conditions only for the photochemical transformations 1 and 2, which are the chief topics of this paper.Because of its representative behavior, methanesulfonyl azide was chosen as the substrate for most of our mechanistic investigations, although the reaction appears general for aliphatic and aromatic sulfonyl azides.Methods and Product Studies. A deoxygenated solution of the azide in peroxide-free isopropyl alcohol was irradiated at ca. 20" with a mercury lamp. The acetone produced was isolated (as its 2,4-dinitrophenylhydrazone) from the distillate of the irradiated solution. The sulfonamide and benzophenone (in those cases where the latter was employed as a sensitizer) were obtained from the distillation residue.A. Direct Photolyses. These irradiations were conducted with unfiltered light in both anhydrous and aqueous isopropyl alcohol. Methanesulfonyl azide, either in the anhydrous solvent or in the presence of 10 vol z water, reacted quantitatively, according to the stoichiometry of eq 1. The photolysis of p-methoxybenzenesulfonyl azide under anhydrous conditions gave the related sulfonamide in at least 9 4 z yield, but the behavior of m-nitrobenzenesulfonyl azide, in (1) (a) Abstracted from the dissertation submitted by M. T. R. in partial fulfillment of the requirements for the degree of Doctor of Philosophy. (b) Presented in summary at the 150th National Meeting of the American Chemical Society, Atlantic City, N. J., Sept 13, 1965, Abstract 23s. (c) This work was supported by the National Institutes of Health (Grants GM-06304 and GM-9693) and by a grant-in-aid from the H. A. B. Dunning Foundation.(2) To whom inquiries should be addressed. (3) H. Kwart and A. A. Kahn, J . Am. Chem. Soc., 89, 1950 (1967), report that the reaction can be effected catalytically with copper.anhydrous solvent, was anomalous. Prolonged irradiation g...

Azide Reactive Dyes

“…Both fixation mechanisms would lead to the formation of a sulphonamide bridging unit between the dye and the nylon substrate. D-SO2 -Nj + H, N-Nylon + D-S02 -NH-Nylon + N3- (6) As nylon substrates are known to contain varying amounts of peroxides, one possible route for furation at low temperatures could involve free-radical decomposition of the azide group, where the peroxide species act as radical initiators [6]. This possibility was ruled out by examining the efficiency of dye-substrate grafting when the substrate was dyed in the presence and absence of an efficient peroxide radical scavenger.…”

Sulfonylative and Azidosulfonylative Cyclizations by Visible‐Light‐Photosensitization of Sulfonyl Azides in THF

“…By using substrates containing terminal alkynes, tetrahydrofurans 10 a-10 c containinge xocyclic alkenylsulfones were produced in 66-88 % yield (entries [11][12][13]. Replacement of the ether tetherw ith a sulfonamidel ed to variousa zacycles 8k, 10 d,a nd 10 e (entries [14][15][16].…”

“…[4d] The formation of a sulfonyl nitrenef rom UV irradiationo fasulfonyl azide with benzophenonea satriplet sensitizer is also known. [14] Furthermore, other electron-deficient azides such as acyl azides and azidoformates are knownt op roduce nitrenes by triplet sensitization with photoactive metal complexes. [4b-d,f] The triplet nitrene 21 could then abstract ah ydrogen atom from THF to give tetrahydrofuran-2-yl radical 15 and sulfonamidylr adical 22.I nr elevant precedent, it is known that triplet sulfonyl nitrenes can abstract ah ydrogen atom from the methine carbon of i-PrOH.…”

“…[4b-d,f] The triplet nitrene 21 could then abstract ah ydrogen atom from THF to give tetrahydrofuran-2-yl radical 15 and sulfonamidylr adical 22.I nr elevant precedent, it is known that triplet sulfonyl nitrenes can abstract ah ydrogen atom from the methine carbon of i-PrOH. [14] Azidation of 15 with the sulfonyl azide would then provide the sulfonyl radical 12 to enter the chain mechanisms shown in Schemes 2a nd 3. The sulfonamidyl radical 22 could then undergo as econd hydrogen abstraction with THF to give para-toluenesulfonamide (23).…”

Radical Chemistry with Azides

“…86 Similar results are obtained by using a radical initiator. 88 The triazenyl radical intermediate undergo a 1,5 -hydrogen transfer coupled to the loss of nitrogen and formation of acetone.…”