Photolytic cleavage ether

Morrison et al. have studied the photolytic cleavage of remote functional groups in the benzonorbornenyl system. Thus irradiation of (163) in methanol at 254 nm yields the reduced product (164a, <(> = 0.12) and the ether (164c, < = 0.13) as the main products, together with the minor products shown in Scheme 10. It is clear from the results that the reactions involve intramolecular... 

A controlled reaction of dichloride (1) with lithium in THF affords dodecamethylsUane, a reagent that has been used for the preparation of sUyl enol ethers through photolytic cleavage. Silanes and polysUanes are readily available from the addition of an organometaUic species to (1) Thus the bisvinylsUane (2) can be prepared from (1) (eq 6). ... 

Three selective methods to remove protective groups are receiving much attention assisted, electrolytic, and photolytic removal. Four examples illustrate assisted removal of a protective group. A stable allyl group can be converted to a labile vinyl ether group (eq. 4) a /3-haloethoxy (eq. 5) or a /3-silylethoxy (eq. 6) derivative is cleaved by attack at the /3-substituent and a stable o-nitro-phenyl derivative can be reduced to the o-amino compound, which undergoes cleavage by nucleophilic displacement (eq. 7) ° ... 

Photolytic. Photooxidation products reported include 2,2 -dihydroxy-4,4 -dimethylbiphenyl, 2-hydroxy-3,4 -dimethylbiphenyl ether, and 4-methylcatechol (Smith et al., 1978). Anticipated products from the reaction of 4-methylphenol with ozone or OH radicals in the atmosphere are hydroxynitrotoluene and ring cleavage compounds (Cupitt, 1980). Absorbs UV light at a maximum wavelength of 278 nm (Dohnal and Fenclov4, 1995). 

Photolytic. The UV photolysis (7, = 300 nm) of bifenox in various solvents was studied by Ruzo et al. (1980). In water, 2,4-dichloro-3 -(carboxymethyl)-4 -hydroxydiphenyl ether and 2,4-di-chloro-3 -(carboxymethyl)-4 -aminodiphenyl ether were identifled. In cyclohexane, 2,4-dichloro-4 -nitrodiphenyl ether and methyl formate were the major products. In methanol, a dichloro-methoxy phenol was identified. Photodegradation occurred via reductive dechlorination, de-carboxymethylation, nitro group reduction, and cleavage of the ether linkage (Ruzo et al., 1980). 

Illustrative examples of the cleavage of support-bound ethers are listed in Tables 3.30 and 3.31. Acidolytic cleavage is the most commonly used strategy, but base-mediated, photolytic, and oxidative cleavage have also been reported. Wang linker... 

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