Azides pivaloyl azide

Pivaloyl azide, 1935 Potassium azidodisulfate, 4655 Potassium azidosulfate, 4653 6-Quinolinecarbonyl azide, 3243... 

The results with carboethoxynitrene are quite different from those obtained with pivaloyl azide 7 and the aroylnitrenes. Furthermore, photolysis of azidoesters 13 and 14 in contrast to pivalolyl and aroylazides at cryogenic temperatures produces persistent nitrene EPR signals. Thus, it is clear that the nitrene esters have triplet ground states. 

The photolysis of acyl azides has also been studied, and in some respects these appear to behave analogously. Pivaloyl azide, for example, adds to cyclohexene to give a 26% yield of an aziridine [Eq. (85)],321 and the assumption is that this addition again occurs via a nitrene. The photodecomposition of acetyl azide (295) in benzo-nitrile and phenylacetylene, on the other hand, affords322 2-methyl-5-phenyl-l,3,4-oxadiazole (296) and 2-methyl-5-phenyloxazole (297),... 

Pivaloyl azide, 1929 Potassium azidodisulfate, 4650 Potassium azidosulfate, 4648 6-Quinolinecarbonyl azide, 3237... 

The difficulties of working with low molecular weight azides are characterized by the preparation of pivaloyl azide (trimetliylacetyl azide)... 

The thermal instability of (pivaloyl azide) prevented elemental analysis. .. Caution pivaloyl azide, like other acyl azides of low molecular weight, has been observed to explode w ithout warning at room temperature. The vapors. . . are quite toxic, and (in some persons) even brief exposure causes rapid pulse, nausea, vertigo, and severe headache. ... 

The photolytic decomposition of carbonyl azides produces generally, but not exclusively, isocyanates " . Lwowski has investigated this photorearrangement in pivaloyl azide He flnds an isocyanate... 

Photolysis of pivaloyl azide in cyclohexene produces 41% isocyanate, 45% JV-pivaloylaziridine (108), T5% of the allylic amide (109), a trace of bi(cyclohex-2-enyl) (110) and some pivalamide (111). 

Lwowski s work on pivaloyl azide has some interesting implications for the mechanism of the photo-Curtius rearrangement photolysis of pivaloyl azide in a variety of solvents results invariably in about 40% isocyanate, irrespective of the medium in which the reaction is conducted. Even in mixed solvents the isocyanate yield is hardly affected... 

Linke, S., Tisue, G. T., Lwowski, W. Curtius and Lessen rearrangements. II. PIvaloyl azide. Journal of the American Chemical Society 1967, 89, 6308-6310. 

Nitrene addition reactions have somewhat more scope when the reactions are carried out by azide photolysis for example, the acyinitrene pivaloylnitrene adds in moderate yield and with good stereoselectivity to cj>alkenes when it is generated from pivaloyl azide by photolysis in dichloromethane." Similarly p-cyanobenzoylnitrene, when generated by photolysis of the azide 21 in the presence of 2,5-dihydrofuian, gives the aziridine 22 in moderate yield (Scheme 6.11)." This nitrene and other p-substituted benzoylnitrenes also react with Cgo to give fulleroaziridines such as 23." ... 

It has been shown that the yield of isocyanates, formed upon photolysis of a series of carbonyl azides (R-CO-N3, R = -Butyl, Aryl), remains constant in the presence and in the absence of nitrene traps.For example, the yield of isocyanate 33a produced on photolysis of pivaloyl azide (R = r-Butyl, 31a) in methylene chloride (an inert solvent) is 40%. Photolysis of 31a in cyclohexene leads to a 45% yield of aziridine adduct 34a and a 41% yield of isocyanate 33a. Trapping the nitrene does not depress the yield of isocyanate. Hence, isocyanate 33a and adduct 34a cannot be derived from the same reactive intermediate, but instead the isocyanate must be formed from the excited state of the azide or from the electronically or thermally excited nitrene. 

Pivaloyl nitrene, generated photolytically from pivaloyl azide, adds to olefins stereospecifically in its singlet state and stereoselectivily in its triplet state. Dichloro-... 

Tetra-O-pivaloyl-a-D-galactopyranosyI Azide (1) Typical Procedure 16... 

D-Galaetopyranovl Azide Tctra-O-pivaloyl- E10b2. 449f. (F - N3)... 

Some sialyltransferases recognize modified CMP-Neu5Ac such as those in which the hydroxyl group at C-9 is replaced with an amido, fluoro, azido, acetamido, or benzamido group [60-63]. Acceptor analogs in which the aceta-mido function is replaced by an azide, phthalimide, carbamate, or pivaloyl functionality are also accepted by the enzyme [64]. 

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