Benzyl alcohol derivatives, electron

Radical cations of dihydropteridines are formed by the photoreduction of lumazine by benzyl alcohol derivatives in the presence of HC104 in acetonitrile, via photoinduced electron transfer to the triplet excited state of the protonated species (11) (Equation (1)) <89CL35>. The unstable photoreduced product has been characterized by its ESR spectrum. 

Reductive cleavage of a C-0 bond requires activation of the bond such activation can be obtained in different ways. Conjugated carbinols, like allylic and benzylic alcohols, tt-electron-deficient heterocyclic carbinols, and a-hydroxyketones and the ethers of these compounds, may be reductively cleaved. Reductive elimination of two vicinal hydroxyl groups or derivatives thereof may also be possible. These reactions have been exploited in the electrochemical removal of protecting groups [40,41]. 

Similarly, chromium-complexed benzylic cations are also stabilized and organic reactions based on the benzylic cation species have been developed. For example, planar chiral o-substituted benzaldehyde dimethylacetal chromium complexes 4 were treated with 3-buten-l-ol in the presence of TiCl4 to give tet-rahydropyran derivatives with high diastereoselectivity (Eq. 5) [5]. The chromium-complexed benzylic oxonium ion 6 would be also generated and subsequent intramolecular cyclization afforded the cyclization product 7. Furthermore, the chromium-complexed benzyl alcohol derivative having electron-rich arene ring at the side chain produced tetrahydroisoquinoline skeleton by treatment with Lewis acid with stereochemical retention at the benzylic position (Eq. 6) [6]. 

Oxygen Nucleophiles. A reagent such as permanganate oxidizes toluene to benzoic acid, whereas benzylic oxidation by palladium acetate results in benzyl alcohol derivatives. The oxidation is favored by electron-releasing substituents in the phenyl ring. Catalytic amounts of palladium acetate and tin diacetate, in combination with air, effects an efficient palladium-catalyzed benzylic oxidation of toluene and xylenes. For the latter substrates, the Q, Q -diacetate is the main product.A mixed palladium diacetate-copper diacetate catalyst has also been found to selectively catalyze the benzylic acyloxylation of toluene (eq 64). ... 

Sub-half-micron features could be resolved with deep-UV (35) and electron-beam (36) radiation with wide process latitude and high sensitivity using this chemistiy. An example of the resolution capability is shown in Figure 4. Very sensitive X-ray and e-beam resist formulations based on similar chemistiy using melamine and benzyl alcohol derivatives as crosslinking agents, formulated with onium salt photoacid generators in novolac or poly(hydrotystyrene) binders, have shown 0.2 fim resolution (30, 31). 

Another approach is based on n-n stacking, which utilizes the moderately strong interactions between delocalized n-electrons of nanocarbons and those in aromatic organic compounds, such as derivatives of pyrene [54,55], porphyrins [56,57], phthalo-cyanines [58] or combinations thereof [59], as well as peptides [60], DNA [61], benzyl alcohol [62] or triphenylphosphine [63]. These molecules are often modified with long... 

The ratio of alcohol to acetate depends upon workup procedure, which differed in the two cases. In addition, acetates of benzylic alcohols typically break down under electron impact by a low energy process to produce ketene and the corresponding alcohol ion. The peak at the parent mass of the alcohol, throughout this work, most likely contains a contribution so derived from the acetate. A careful distinction between the alcohol and acetate was not deemed important for our purposes, so... 

HA compounds is not necessary for the formation of a polyester. Nevertheless, an acceleration effect of HA compounds on the rate of copolymerization was detected later 36 57 74), even for systems in which proton donors are directly bound to monomers 67). This effect is not the sum of the contributions from the tertiary amine and the proton donor but even stronger. Hence, proton donors display a cocatalytic effect. Concerning the effect of HA compounds Tanaka and Kakiuchi 36) established a linear correlation between Hammett s ct constants and the logarithm of the gelation time for various substituted derivatives of benzoic acid, benzyl alcohol and phenol, and positive reaction parameters q were found in all cases. This means that electron-withdrawing substituents increase the effect of HA compounds, or their effect becomes more pronounced with increasing hydrogen atom acidity. 

Although considered mild in comparison with other metals, copper(I) and (II) Inflates are suitable Lewis acids for affecting Friedel-Crafts alkylation and acylation reactions (Sch. 22). The intramolecular acylaminoalkylation of the indole derivative 88 afforded the cyclized product 89 in high yield [49]. The nitrogen functionality was not a requirement for formation of the benzylic cation, because the benzylic alcohol 90 reacted similarly with 91, even with an electron-withdrawing ester group adjacent to the cationic center. 

Reactions of organosamarium(II) halides with aldehydes are sranewhat more complicated and synthetically less useful than those with ketones. The ability of Sm species to serve as strong reducing agents introduces a number of alternative reaction pathways. For example, reaction of EtSmI with benzalde-hyde provides a mixture of benzyl alcohol, benzoin, hydrobenzoin, and benzyl benzoate in low yields. Die first three products presumably arise from benzaldehyde ketyl, generated by single-electron transfer from the Sm reagent to benzaldehyde. The benzyl benzoate apparently is derived frmn a Tischenko-type condensation reaction between a samarium alkoxide species and benzaldehyde. 

Palladium-catalyzed cyclopropanation using diazomethane has been achieved stereoselectively on a series of a,)9-unsaturated carboxylic acids derivatized with camphorsultam as a chiral auxiliary. The selectivity of the reaction produces cyclopropanated products 22 with the absolute configuration. The stereoselectivity of the reactions is temperature dependent. Several A-enoylsultams 21 were successfully cyclopropanated in this manner. It was found that branching at the a- or /i-carbons disfavors complete conversion an electron-withdrawing substituent at the )9-position is particularly unfavorable. The chiral auxiliary was removed by using titanium(IV) isopropoxide in benzyl alcohol followed by alkaline hydrolysis of the intermediate ester providing cyclopropanated derivatives 23b of high diastereomeric purity. ... 

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