1-naphthyl-, photolysis

The halide groups can be replaced by other substituents like hydride or alkyl [86]. When the naphthyl (np) RuHnp(dmpe)2 is heated, the ligand undergoes an internal metallation to afford a dimer [87] (it was originally believed to be a monomer), though Ru(dmpe)2 has been isolated by photolysis of its dihydride, in matrixes at 12K (Figure 1.29) [88],... 

Similiar to the case of bicyclo[4.1.0]heptatriene (2a), the proposed31 bi-cyclic intermediate (2b) in the ring expansion of lb has never been directly observed. However, the analogous azirines, formed by photolysis of 1- and 2-naphthyl azides, have been characterized by IR (Scheme 13)47 and both trapping48 3,6,0 and IR spectroscopic characterization484 of substituted derivatives... 

The crucial requirement of excited-state proton transfer (ESPT) is suggested by the failure of 1-naphthyl methyl ether to undergo self-nitrosation under similar photolysis conditions. The ESPT is further established by quenching of the photonitrosation as well as 1-naphthol fluorescence by general bases, such as water and triethylamine, with comparable quenching rate constants and quantum yield. ESPT shows the significance in relation to the requirement of acid in photolysis of nitrosamines and acid association is a photolabile species. 

From photoreduction (> 280 nm) in diethylamine, low yields of 1-naphthyl-amine and the corresponding azo- and azoxy compounds have been obtained Photolysis (366 nm) in acidified 50% aqueous 2-propanol at varied HCl-concentrations results in remarkable enhancement of photoreduction compared to neutral 2-propanol. The highest disappearance quantum yield measured was 1.28 X 10 2 for 6 M HCl 4-chloro-l-naphthylamine is formed as main product 74.75). 

In arylcarbenes not only the internal bond angle but also the dihedral angle between the bond plane and the aryl plane can be bent. Photolysis of a- and /S-naphthyl-diazomethanes in a matrix gave two isomeric carbenes, which produced different ESR signals >. 

Further evidence for the generation of acyl radicals is the formation of benzaldehyde on photolysis of benzoyl-1-naphthyl telluride in the presence of thiophenol. 

Photolysis of the telluroester in the presence of thiophenol isolation of benzaldehyde. A solution of the telluroester (Ar = 1-naphthyl) (15 mg, 41.7 jjmol) and thiophenol (17 mg, 154 jjmol) in CDCI3 (0.6 mL) was photolysed with a 250 W white light source at 8°C for 2 h. Preparative TLC on silica gel of the reaction mixture, eluting with ethyl acetate/hexa-nes, 1 9, gave benzaldehyde (3.5 mg, 80%). 

The reactivity of acyl radicals inside and outside the solvent cage has been a matter of discussion. It has been postulated that aryloxy and acyl radicals could disproportionate within the cage to give phenol (or naphthol) and ketene (37) but the results are not conclusive (Scheme 14). On the one hand, photolysis of 1-naphthyl acetate in a solvent without abstractable H-like Freon 113 (1,1,2-trichl-oro-l,2,2-trifluoroethane) yields low amounts of 1-naphthol (< 0.1%) in comparison with the same reaction in acetonitrile (7%) [50]. This reveals that dispropor-... 

Photolysis of 2-naphthyl thioesters in the presence of a hydrogen donor such as 1,4-cyclohexadiene yields aldehydes (80-100%) no photo-Fries reaction products have been reported [60],... 

Nakamura and co-workers provided detailed mechanistic information for the photoinduced electron transfer from tri-1 -naphthyl phosphate and related compounds to 9,10-dicyanoanthracene yielding binaphthyls The intramolecular nature of the reaction could be established by using laser flash photolysis experiments as well as fluorescence measurements [17],... 

A reaction which could involve the vinyl alcohol tautomer of acetaldehyde is the synthesis of 2-(2-naphthyl)quinoline by photolysis of the anil (393) in ethanol (68TL3685). From the benzaldehyde anil of a-naphthylamine by a similar reaction, 2-phenylbenzo[Jt]quinoline... 

The nature of the intermediate involved in the thermolysis and photolysis of aryl azides in solution under the much less extreme conditions employed for the synthesis of 3H-azepines is still an open question. Notwithstanding, the method has been used extensively for the synthesis of 2-amino-3H-azepines. In addition, and despite early disappointments, the method is now applicable to the synthesis of benzazepines from naphthyl azides and that of pyridoazepines from quinolyl and isoquinolyl azides <82JCS(Pl)43l, 79AG(E)900). 

Photolysis of the 8-azido-l-arylazonaphthalene (531 Ar = 2-methoxy-l-naphthyl) gives a low yield (5%) of the betaine (321 Ar = 2-methoxy-... 

Another example of the effect of confined medium is found during photo-Fries rearrangement of naphthyl esters in zeolites [103,104]. Upon photolysis in isotropic solution 1-naphthyl benzoate undergoes the photo-Fries rearrangement to yield both ortho (2-) and para (4-) phenolic ketones (Sch. 4). When this ester is included in NaY zeolite and irradiated the main product (96%) is the ortho isomer. This remarkable ortho-selectivity within zeolites has been rationalized on the basis of interactions of the reactant 1-naphthyl benzoate and intermediate radicals with the sodium ion. Due to restrictions imposed by the medium the benzoyl radical, once formed, is compelled to react only with the accessible ortho position. 

An impressive illustration of the influence of the medium on the photo-Fries reaction product distribution can be found in Sch. 5 where the products of photolysis of 1-naphthyl 2-methyl 2-phenyl propanoate in hexane solution and within NaY are compared. Remarkably, whereas in solution eight products are formed, within NaY zeolite a single product dominates the product mixture. Cations present within zeolites help to anchor the reactants, intermediates and products to the surfaces of the zeolite and... 

Intramolecular carbenoid and nitrenoid insertions are also quite effective for the preparation of peri-condensed heterocycles. Thus, photolysis of 1-naphthyl-1,2,3-triazoles 113 leads to bcnzo[d,e quinolines 115, possibly via carbene intermediate 114 (Scheme 55) <1987J(P1)413>. Similarly, on photolysis or thermolysis of 8-azido-l-arylazonaphtha-lenes 116 naphtho[l,8-<7, ]triazine derivatives 117 are formed along with A-aryhminobenzo[/y/]indazoles 118 (Scheme 56) <1978JOC2508, 1982JOC1996>. 

The effect of wavelength on the (piantum yield of CO production from the photolysis of CII2CO can be satisfactorily interpreted on the basis of the RE.K model, but unfortunately the lack of data on the precise bond dissociation energy prevents a uiiiciuc assignment of parameters. The wavelength dependence of the fluorescence of photoexcited /3-naphthyl-amine has also been reasonably well interpreted in terms of the rate of spontaneous isomerization to a inetastable state incapable of fluorescence. A model for k E) equivalent to the RRK model was used. 

Dihydrobenzoxanthenes 27 result from the photolysis of 2-(l-naphthyl)phenols a quinone methide intermediate is postulated. The twisted nature of the o-hydroxybiaryl system facilitates excited-state intramolecular proton transfer (ESIPT) at both the 2 - and 7 -positions <03JA1164>,... 

Phosphorescence studies in isobutylene-methyl methacrylate-1-naphthyl-methyl methacrylate co-polymer provided evidence to show that in very dilute solution the chain collapses into more compact structures, and intramolecular excimer formation in poly-(2-vinylnaphthalene) has been shown to exhibit non-Stokes-Einstein behaviour. Laser photolysis of polymers containing phenanthryl groups, such as poly-(9-vinylphenanthrene), indicates the presence of plural dimer sites having different geometries owing to the stacking effect of phenanthrene chromophores. In poly-(2-naphthyl methacrylate). 

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