Allylic alcohols, photolysis

At elevated temperatures of 60-100 °C, jr-allyl complexes will react with water to give aldehydes or ketones (equation 58). The mechanism probably involves attack of OH on the coordinated r-allyl, and elimination of Pd-H to generate the aldehyde group. Molecular bromine cleaves TT-allyl-palladium bonds to give allylic bromides. Peracids have been reported to convert r-allyl complexes into allylic alcohols. Photolysis of r-allyl complexes in the presence of oxygen results in the conversion of an allylic group into an a, /3-unsaturated ketone. 

Allyl silanes react with epoxides, in the presence of Bp3-OEt2 to give 2-allyl alcohols. The reaction of a-bromo lactones and CH2=CHCH2Si SiMe3)3 and AIBN leads to the a-allyl lactone. " Benzyl silanes coupled with allyl silanes to give ArCH2—R derivatives in the presence of VO(OEt)Cl2 " and allyltin compounds couple with allyl silanes in the presence of SnCU. " Allyl silanes couple to the a-carbon of amines under photolysis conditions. ... 

Metallocyclopentenes are frequently formed in photochemical reactions of the Group 14 metal alkyls or catenates in the presence of dimethylbutadiene. This class of compound also has an extensive photochemistry82. For example, photolysis of 51 (R = H or Me) produced the allylic alcohols 52 and 53 and, for R = H, 54. These alcohols could be dehydrated over AI2O3 to give the germole 55 along with other diene compounds. 

Photolytic. Atkinson (1985) reported a rate constant of 2.59 x 10 " cmVmolecule-sec at 298 K. Based on an atmospheric OH concentration of 1.0 x 10 molecule/cm , the reported half-life of allyl alcohol is 0.35 d. The reaction of allyl alcohol results in the OH addition to the C=C bond (Grosjean, 1997). In a similar study, Orlando et al. (2001) studied the reaction of allyl alcohol with OH radicals at 298 K. Photolysis was conducted using a xenon-arc lamp within the range of 240-400 nm in synthetic air at 700 mmHg. A rate constant of 4.5 x 10 " cm /molecule-sec was reported. Products identified were formaldehyde, glycolaldehyde, and acrolein. 

Photolytic. Distilled water irradiated with UV light (X = 290 nm) yielded the following photolysis products 2-chloro-l-propanol, allyl chloride, allyl alcohol, and acetone. The photolysis half-life in distilled water is 50 min, but in distilled water containing hydrogen peroxide, the half-life decreased to <30 min (Milano et al, 1988). 

Prior to the work of Cheng et al. Rubin et al. reported a similar [4 + 4] pho-tocyclization reaction [299]. Rubin has shown that a cyclohexadiene derivative underwent a very facile photochemically promoted rearrangement to the stable bridged bisfulleroid 198 (Scheme 76). This process occurs via the initial [4 + 4] photoadduct (not observed), which undergoes a thermally allowed [2 + 2 + 2] cycloreversion to afford a bis-methano[12]annulene structure 198. Alternatively, compound 198 can be obtained by photolysis of the allylic alcohol 197 under reflux and acidic conditions in good yields. The allylic alcohol is obtained by acidic... 

Although, the photolysis requires quite short wavelengths (254 nm), the reaction is clean and high-yielding (up to 84% of liberated alcohol) in acetonitrile (a different and nonproductive reaction occurs in benzene) with a variety of primary, secondary, and allylic alcohols, as well with 3 - and 5 -protected nucleosides. The chemical stability is very high, approaching that of triisopropylsilyl (TIPS) in some cases (R2 = Me). 

Photolysis of PhI(OAc)2 with tertiary allylic alcohols 590 in the presence of iodine affords a-iodoepoxides 591 (50-72% yield) as a result of alkoxy radical rearrangement (Scheme 3.233) [632]. 

C3H50]- Photolysis of H2O2 in allyl alcohol/ EPR/ 66Livl/... 

Radical Coupling and Cyclization Reactions. Phenyl thionocarbonate esters derived from alcohols serve as efficient precursors for the generation of radical intermediates which can be used for the formation of new carbon-carbon bonds. For example, a 4-thionocarbonate ester derived from L-lyxose undergoes a stereoselective allylation upon photolysis in toluene in the presence of 2.0 equiv of allyltributylstannane (eq 6). Photochemical initiation is preferable to chemical initiation using azobisisobu-tyronitrile which results in the formation of side products at the... 

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