924. An attempt to study reactions of the free benzoyl radical: reactions of azodibenzoyl and related compounds

Abstract

Oxidation of benzoyl-and dibenzoyl-hydrazine with silver oxide or thermal decomposition of azodibenzoyl in solution gives inconclusive indicactions of the production of free benzoyl radicals. Much better evidence of the formation of free aroyl radicals has been obtained from studies of the photolyses of both azodibenzoyl and p-nitroazodibenzoyl in solution which show that the radicals react by dimerisation and by addition to undecomposed substrate in preference to attacking the surrounding solvent. Reaction schemes are proposed to account for the formation of the main reaction products.Oxidising actions and Diels-Alder condensations of azodibenzoyl are also reported.THIS work was planned as a study of the reactivity of the free benzoyl radicals by using processes which, unlike the homolytic chain reaction of benzaldehyde, do not involve competitive reactions of other radicals. Reactions of free alkyl radicals of a single type

Novel visible light activated type 1 photosensitizers

“…The classes of photosensitizers described herein contain azido (-N=N=N), azo (-N=N-), and oxaza (-N-O-) functional groups that have long been known to undergo photofragmentation give nitrenes and free radicals. [26][27][28][29][30][31][32][33][34] …”

The Effect of Bridge Size on the Sigmatropic Rearrangement of 2,3-Dibenzoyl-2,3-diazabicyclo[2.2.n]alk-5-enes

“…Further increase in n could permit the tetrahydropyridazine to pass into the lower energy pseudo chair form, which would then resemble in stability the simple unbridged adduct 7 of butadiene. All efforts to isomerize 7 (14), alone or in the presence of acid, at temperatures up to 350" failed (above this it charred and decomposed). The thermal stability of 7 seems reasonable in the light of the known (15) high barrier to ring inversion for this ring system (-I5 kcal mol-'), which must be surmounted as a prerequisite to the boat form from which reaction can be initiated.…”

Synthesis and Isomerization of Adducts of Azodicarbonyl Compounds and Cyclopentadiene

“…Compound 2a was obtained by oxidation of the mercury-(11) salt of 1,2-di-p-bromobenzoylhydrazine (20) with bromine in carbon tetrachloride (2 Azodi-p-nifrobenzoyl Oxidation of the mercury salt of 1,2-di-p-nitrobenzoylhydrazine (22) with bromine in methylene chloride gave the sparingly soluble azodi-p-nifrobenzoyl which was precipitated from its solution by addition of pentane as a yellow solid, m.p. 157" (dec.).…”

“…We have recently shown (1) that the thermal isomerization of the cyclopentadiene adduct 16 (2) gives, as suspected (3), the racemic 1,3,4-oxadiazine derivative lc,d. The isomerization was cleanly first order, was relatively insensitive to solvent character, had a negative entropy of activation, and thus possessed all the features of a [3,3] sigmatropic process (4).…”

“…All of the azo compounds 2a-12a required for the present study were obtained by oxidation of the appropriate dicarbonylhydrazine with Nbromosuccinimide (NBS) in the presence of pyridine (5) or by oxidation of the mercury(I1) salt of the hydrazine with bromine (2). Only 3a, 7a, 9a, and 12a (6-9) have been previously 'On the basis of time-averaged conformational processes.…”