Diazides, photolysis

Other recent applications of the diazide photolysis route include the matrix isolation of some interesting cyclic silylenes (equations 23 and 24)54,55. Solution photolysis of diazides can give other reactive species in addition to silylenes. 

Two crosslinks per macromolecule are needed to make a polymer insoluble. Quantum yield of a diazide photolysis is ca. 0.5, therefore, the critical dose of the photochemical polymer insolubilization should be about 50mJ/cm. ... 

An elegant extension of these ring expansions involving diazidonaphthalenes has been reported. Early results on the photolysis of 1,8-diazidonaphthalene (14) indicated the formation of benz[t d]indazole (17).176 However, it has since been found that photolysis of the diazide in sodium methoxide-methanol/dioxane solution for a short period (20 -40 min) yields, in addition to the benz[c,d]indazole (17, 40%), a mixture of 9-azido-l-methoxy-5//-2-benzazepine (15 15-20%) and l,10-dimethoxy-5,5a-dihydroazepino[3,4-c]azepine (16 10-15%).117... 

The photolysis of o-quinone diazides was carefully investigated by Stis in 1944, many years before the development of photoresists. Scheme 10-102 shows the photolysis sequence for the diazoquinone 10.75 formed in the diazotization of 2-amino-1-naphthol. The product of the photolytic step is a ketocarbene (10.76), which undergoes a Wolff rearrangement to a ketene (10.77). In the presence of water in-dene-3-carboxylic acid (10.78) is formed this compound is highly soluble in water and can be removed in the development step. The mechanism given in Scheme 10-102 was not postulated as such by Stis, because in 1944 ketocarbenes were unknown (for a mechanistic discussion of such Wolff rearrangements see review by Zollinger, 1995, Sec. 8.6, and Andraos et al., 1994). 

Tsuda and Oikawa (1989) investigated the photolysis of the 1,2-isomer of 10.89 (1,2-benzoquinone diazide) by means of MINDO/3 molecular orbital calculations with configurational interaction. These authors came to the conclusion that no ketocarbene of the type of 10.90 is formed, but that the rearrangement into the cyclopentadienyl ketene 10.94 is a concerted reaction in which the elimination of nitrogen and the rearrangement take place simultaneously. In the opinion of the present author the theoretical result for 1,2-quinone diazide is not necessarily in contradiction to the experimental investigations of Sander, Yankelevich et al., and Nakamura et al., as the reagents used were not exactly the same. 

Laser flash photolysis (LFP) of quinone diazide 2d in Freon-113 at room temperature produces carbene Id, which could be monitored indirectly by addition of trapping reagents.25 At 2.0 xs the lifetime of Id is slightly longer than that of la (1.65 xs), otherwise the reactivities of these carbenes are very similar. The Id —> 11 rearrangement is not observed in the LFP experiments. All trapping products with a variety of reagents (O2, acetonitrile, pyridine etc.) are derived from carbene Id. 

The photolysis of benzo-annellated quinone diazides such as 2m should preferentially lead to products with intact benzene rings. Monochromatic irradiation... 

Miura and Kobayashi studied the photochemistry of 4,4-biphenyl bisazide. They concluded that photolysis of this diazide leads to extrusion of a single molecule of nitrogen with the formation of a singlet state species, X , with a lifetime of 19 ns. Miura and Kobayashi did not specify the nature of X. This species absorbs at 380 nm and its spectrum and lifetime are similar to our results with singlet para-biphenylnitrene. Therefore we conclude that X is singlet 4 -azido-4-biphenylnitrene. 

Photolysis of o-quinone diazides may be accompanied by dimer227- formation, e.g., in the case of CCVI and CCVII.270,271... 

The light-induced reaction of o-quinone diazides finds occasional use in the synthesis of a large number of compounds which are used in photography.273,277 Photolysis of diazoindauoues (CCVIII and CCX) provides a new synthetic route to cyclobutene carboxylic acid derivatives CCIX and CCXI, respectively.117 A good demonstration that ketenes are actually involved in the photodecomposition of o-quinone... 

Photosynthesis of azo-dyestuffs has been reported to be effected by the irradiation of o-quinone diazides. The reaction proceeds via the contraction of the diazide CCXV to the cyclic ketene CCXVI which adds water to form the eyclopentadiene carboxylic acid CCXYII. The latter couples with unchanged CCXV (obtained from 2-amino-l-phenol-4-sulfonic acid) to form the azo-dyestuff CCXVTII.270 Similarly, V-heterocyclic azo-dyestuffs, e.g., CCXX is obtained by the photolysis of CCXIX.275... 

The photolytic process of p-quinone diazides are of great interest since they establish a synthetic route for the preparation of a large number of phenolic compounds. CCXXII and CCXXIV are obtained on irradiation of p-quinone diazide (CCXXI) and imino-p-quinone diazide (CCXXIII) in the presence of primary alcohols,279 respectively photolysis of CCXXI in water produces hydroquinone.137 Another well-authenticated example of this reaction, is the photodecomposition of CCXXI and CCXXIII in the presence of benzene, and 2,6-dichloro-quinoneimine diazide-4 in the presence of pyridine to CCXXV, CCXXVI, and CCXXVII, respectively. 

A related silylene, the four-membered ring 57b prepared by photolysis of the corresponding diazide, was reported by Veith and coworkers to decompose at very low temperatures55. 

The carbene mechanism of heterolytic dehalogenation of 4-chlorophenol was subsequently confirmed by studies using flash photolysis [21] and FT-EPR [22], A detailed account of the EPR measurements was published later [23], in which it was shown that the spin polarization of the phenoxyl-propanoyl radical pair produced in the photolysis of 4-chlorophenol in 2-propanol is consistent with a triplet state precursor. The proposition that this precursor is the above-mentioned carbene was proved by generating the same radical pair, with identical spin polarization, by photolysis of p-benzo-quinone diazide [22,23]. 

Carbena-cyclohexadienone (3). Photolysis or thermolysis of -quinone diazides (15) easily led to 3. The precursors of 3 are either />-aminophenols (14), -quinones (77) or anthrones (76). Diazotization of 14, Bamford-Stevens reaction of the tosyl-hydrazone of 77, or diazo-group transfer to 76 afforded the corresponding -quinonediazides 15 31-84)... 

The photolysis of aromatic diazides in the solid phase leads to the formation of dinitrenes in a consecutive manner, viz. 

QUANTUM YIELDS OF PHOTOLYSIS OF AROMATIC DIAZIDES AT 77 "K IN A METHYLCYCLOHEXANE-ISOPENTANE MATRIX... 

Photolysis of phenyl and o-trifluoromethylphenyl azide in solid matrices led to the triplet nitrene as detected by e.s.r. The actual processes involved in aromatic azide photolyses have been the subject of much studyThe electronic spectra of the nitrenes were measured by photolysis of a number of aryl azides in organic matrices at 77°K . These species were stable indefinitely at this temperature, no change being observed in the spectra for hours. The photolysis of diazides at 77°K, whether conjugated (e.g. / -diazido-benzene) or not [e.g. bis (j6-azidophenyl) methane] proceeded in two distinct steps to the dinitrene. The second step was about two to three times as efficient as the first ( 2/ 1 2-3)... 

An interesting reaction was discovered by Moriarty in the photolysis of the geminal diazide, dimethyl diazidomalonate (28) Irra-... 

Wasserman and co-workers investigated the photolysis of benzo-phenone diazide (31) in a rigid matrix at 77°K by observing the e.s.r. spectra of the photoproducts. At the onset of irradiation the signal of an azido nitrene appeared, prolonged photolysis resulted in diphenyl-methylene radicals. Irradiation of benzophenone diazide (31) in benzene solution at normal temperature produced 2-phenyl-benzimidazole (32) in 52% yield, together with 1,5-diphenyltetrazole (33) and diphenyl carbodiimide trimer (34). Irradiation of the tetrazole (33) produced only the imidazole (32) but no trimer (34) indicating that the imino nitrene intermediate formed by irradiation of 33 was different from the one produced directly in the primary photolysis of benzophenone diazide (31). No products of a diphenyl-methylene precursor were isolated. 

Quinone diazides such as (104) are readily prepared by nitrosation of 4-aminophenols. On photolysis, (104) smoothly cyclizes to (105), a model for the antitumor antibiotic CC-1065 (equation 43). ... 

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