Thermolysis of Acylazo O-Trimethylsilyl Cyanohydrins:  Azoalkanes Yielding Captodatively Substituted Radicals

Abstract

A new synthetic method has been developed for preparing azoalkanes bearing geminal α-cyano and α-trimethylsiloxy groups. While the symmetrical compound 5 decomposes near room temperature to afford, almost entirely, the C−C dimers, the unsymmetrical azoalkane 3 requires heating to 75 °C. The thermolysis activation parameters of 3 and 5 can be rationalized on steric grounds without invoking captodative radical stabilization. A 13C NMR product study of photolyzed 3 in the presence of TEMPO at 21 °C shows that the fate of caged [tert-butyl, 1-trimethylsiloxy-1-cyanoethyl (14)] radical pairs is disproportionation, 17%, cage recombination, 20%, and cage escape, 63%.

Azobenzenes—synthesis and carbohydrate applications

“…The preparation of azobenzene derivatives has been reported by a stoichiometric oxidation process of hydrazo compounds using H 2 O 2 , 72 O 2 , 73 MnO 2 , 19 sodium hydroxide, 74 triarylphenol/potassium ferricyanide/sodium hydroxide, 75 iron chloride, 76 periodate resin, 77 Pb(MeCO 2 ) 4 , 78 HgO, 79 (NH 4 ) 2 S 2 O 8 , 80 N-bromosuccinimide in pyridine, 81 tetrabutylammonium cerium(IV) nitrate 82 and arylsulfonyl peroxide reagents, 83 NaNO 2 in acetic anhydride, 84 polyethylene glycol/nitrogen dioxide, 85 and NaNO 2 /NaHSO 4 on silica support. 86 The oxidation of hydrazine derivatives using H 2 O 2 as oxidant was studied.…”

3‐Rhoda‐1,2‐diazacyclopentanes: A Series of Novel Metallacycle Complexes Derived From CN Functionalization of Ethylene

“…We next aimed to prepare complex [17] + independently by insertion using complex [1] + and diacetyl diazene (AcN=NAc), which was prepared through oxidation of diacetyl hydrazine. [32] Addition of AcN=NAc to a solution of [1] + in CH 2 Cl 2 at room temperature provided a deep orange solution, which was stirred for 2 h. Satisfyingly, ESI(+)-MS of the crude reaction mixture showed two distinct signals at m/z 507 and 535 (also observed for [17] + ) for the coordinated azo compound and ethylene insertion product, respectively (Scheme 6). However, the 1 H NMR spectrum of this mixture did not contain signals attributable to [17] 13 C{ 1 H} and 1 H-13 C{ 1 H} HSQC NMR spectroscopy confirmed this assignment, illustrating that both doublet signals were bonded to the same sp 2 carbon at 126.0 ppm.…”

“…[32] Addition of AcN=NAc to a solution of [1] + in CH 2 Cl 2 at room temperature provided a deep orange solution, which was stirred for 2 h. Satisfyingly, ESI(+)-MS of the crude reaction mixture showed two distinct signals at m/z 507 and 535 (also observed for [17] + ) for the coordinated azo compound and ethylene insertion product, respectively (Scheme 6). However, the J Rh,C = 3.2 Hz)-an anticipated feature provided the adjacent N atom was coordinated to Rh.…”

The electrochemical reduction of 1,4-dichloroazoethanes: Reductive elimination of chloride to form aryl azines

“…The azo (N N) bond is a relatively labile group often accompanied by the loss of N 2 under a variety of thermal and photochemical conditions [1][2][3][4][5][6][7]. The fragmentation of the C-N bond is rationalized to occur by homolytic cleavage upon photolysis via a radical pathway [4][5][6][7][8].…”

“…The fragmentation of the C-N bond is rationalized to occur by homolytic cleavage upon photolysis via a radical pathway [4][5][6][7][8]. Conversely, the electrochemical reduction of azo compounds in aprotic solvents generally involves two sequential one-electron reductions of the N N to the radical anion and dianion, respectively [5].…”