Benzyl alcohol, from oxidation

Primary benzylic alcohols are oxidized to aldehydes in good yields without overoxidation (entry 1) lowering the pH from 5 to 3.5 increases the conversion, for reasons not fnUy understood yet (entry 2) . The aminoxyl radical is an electrophilic species" ... 

The oxidation of alcohols to aldehydes can also be accomplished by benzeneseleninic anhydride, (0 115860)20, either as such [525] or prepared in situ from diphenyldiselenide, (0 115)2862, and rert-butyl hydroperoxide [1140]. Benzylic alcohols are oxidized more rapidly than allylic... 

In continuation of this study. Farmer and Welton investigated the selective oxidation of alcohols to aldehydes and ketones by TRAP in conjunction with eithCT A-methylmorpholine-N -oxide or molecular oxygen as oxidants [40]. In the case of molecular oxygen (as oxidant), Cu(I) and a diamine ligand must also be added. Under the optimized conditions, benzylic alcohols were oxidized in good to excellent yields, whereas aliphatic alcohols required longer reaction time and gave poor yield. The reaction products were easily removed from the reaction mixture by extraction with diethyl ether. 

Isoindoles can be produced by eliminations from A-substituted isoindolines (1,3-dihydro-isoindoles), themselves readily produced by the reaction of a nitrogen nucleophile and a l,2-bis(bromomethyl)-benzene examples are the pyrolytic eUmination of acetic acid from the cyclic hydroxylamine acetate,or, at a much lower temperature, of benzyl alcohol from an A-hydroxy-isoindoline benzyl ether, or of methanesulfonic acid from a corresponding mesylate. A-substituted isoindoles, too, have generally been made from an isoindoline by elimination processes, thus A-oxides can be made to lose water by pyrolysis," or better, by treatment with acetic anhydride. ... 

Benzyl alcohols are oxidized to aromatic aldehydes by nitric acids using Yb(OTf) as catalyst. Byproducts from this reaction are water and nitrogen oxides only. 

An interesting example of this type of chemoselective oxidation has been reported with die reagent mixture derived from diisopropyl sulfide and iV-chlorosuccinimide. This reagent will oxidize selective ly a primary alcohol to an aldehyde at 0 C. Surprisingly, this same reagent at -78 C will oxidize selec lively a secondary alcohol to the corresponding ketone (Scheme 2). Allylic and benzylic alcohols are oxidized at both temperatures. 

Dimethoxybenzyl esters prepared from the acid chloride and the benzyl alcohol are readily cleaved oxidatively by DDQ (CH2CI2, H2O, rt, 18 h, 90-95% yield). A 4-methoxybenzyl ester was found not to be cleaved by DDQ. The authors have also explored the oxidative cleavage (ceric ammonium nitrate, CH3CN, H2O, 0°, 4 h, 65-97% yield) of a variety of 4-hydroxy- and 4-amino-substituted phenolic esters. ... 

It appeared that the impure alcohol isolated from balsam of Peru was, in fact, identical with nerolidol. When allowed to stand for three to four weeks with phenyl-isocyanate both alcohols yielded a phenyl-urethane, melting at 37" to 38°. A mixture of the two bodies suffered no depression in melting-point. The alcohols have the formula 15 260-The alcohol from balsam of Peru is therefore mixed with a small quantity -of an alcohol of higher specific gravity, the nature of which is still undetermined. Traces of benzyl alcohol were found in it, but not in sufficient quantity to account for the differences observed. Oxidation experiments did not throw any light on the question. It may therefore be safely assumed that the peruviol of Thoms consisted in the main of nerolidol, but contaminated with a substance of the same boiling-point to such an extent that its combustion figures pointed to the formula CjjH. jO instead of... 

C ( propyl) N phenylmtrone to N phenylmaleimide, 46, 96 semicarbazide hydrochloride to ami noacetone hydiochlonde, 46,1 tetraphenylcyclopentadienone to diphenyl acetylene, 46, 44 Alcohols, synthesis of equatorial, 47, 19 Aldehydes, aromatic, synthesis of, 47, 1 /3-chloro a,0 unsaturated, from ke tones and dimethylformamide-phosphorus oxy chloride, 46, 20 from alky 1 halides, 47, 97 from oxidation of alcohols with dimethyl sulfoxide, dicyclohexyl carbodumide, and pyndimum tnfluoroacetate, 47, 27 Alkylation, of 2 carbomethoxycyclo pentanone with benzyl chloride 45,7... 

The final residue from the mother liquor is an oil which does not solidify in a freezing mixture, and appears to be a mixture of p- and w-tolylcarbinols. Only a trace of phthalic acid (phenolphthalein test) was obtained by oxidizing this oil with permanganate the portion of it which was more readily soluble in water yielded a phenylurethan which depressed the melting point of the phenylurethan of either />-tolylcarbinol or benzyl alcohol. 

We have also found that BTMA Br3 can be used as a reagent for the oxidation of benzyl alcohols to benzoic acids. That is, the reaction of benzyl alcohols with 2-equiv. of BTMA Br3 in an aq. alkaline solution at room temperature or at 70°C afforded benzoic acids in good yields. Thus, we could selectively obtain the oxidation products, benzaldehydes and benzoic acids, from benzyl alcohols by using a stoichiometric amount of BTMA Br3 (Fig. 24) (ref. 32). 

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