Benzylidene diacetate

Benzyl alcohol, oxidation, by ruthenium oxo complexes, 39 287-289 Benzylazide, NMR of, 4 263 Benzylidene diacetate, nitration of, 6 114 Berkelium... 

In a reaction somewhat similar to the Cr02Cl2 oxidation, Cr03 in AcOH in the presence of mineral acids produces benzylidene diacetates, which can then be hydrolyzed to the corresponding aldehydes.110,693,798 Cr(V) and Cr(IV) species were shown to be involved in the reaction.798 Silver(II) in acidic solution,845 Ce(NH3)2(N03)6,846 and photooxidation in the presence of Ti02 and Ag2S04847 are also used to accomplish aldehyde formation. 

It represents a convenient method for the synthesis of benzyl esters from methylbenzenes. Small amounts of benzylidene diacetates are formed at high conversions. 

Toluene was oxidized to a mixture of benzyl acetate (31) and benzylidene diacetate (32) on reaction with oxygen in the presence of a silica supported Pd-Sn catalyst.A reaction run in HOAc/KOAc at 70°C under an atmosphere of oxygen gave a near 3 1 ratio of the monoacetate to the diacetate at 98% conversion (Eqn. 21.40). The two products are formed in parallel reactions as the benzylacetate does not react further under these reaction conditions. Substituted diphenylmethanes were oxidized to the diphenyl ketones by refluxing them in air in a DMF solution containing a copper powder catalyst.""... 

Benzylic oxidation of toluenes. Toluene is oxidized by palladium acetate (equimolar) in acetic acid at 90° (13 hrs.) to benzyl acetate (80% yield), benzaldehyde (4%) and benzylidene diacetate (6%) with formation of palladium (O).4 This oxidation is sensitive to electronic factors. Thus p-methoxytoluene is converted in 96% yield into p-methoxybenzyl acetate whereas p-nitrotoluene is essentially inactive. 

Interestingly, the authors reported that benzyl acetate was not further oxidized under the reaction conditions, suggesting that benzylidene diacetate is formed in a parallel rather than consecutive reaction. 

In 212 cc of water are mixed 21.2 grams (0.112 mol) of N-(benzylidene)-3-amino-2-oxa-zolidone, 8.93 grams of concentrated sulfuric acid, and 30.1 grams (0.124 mol) of 5-ni-tro-2-furaldehyde diacetate. This mixture is heated to effect the hydrolysis of N-(benzy-lidene)-3-amino-2-oxazolidone, steam distillation of the benzaldehyde and hydrolysis of 5-nitro-2-furaldehyde diacetate. Approximately IV2 hours are required for this reaction to take place. When the bulk of the benzaldehyde has been removed, 50 cc of 99% isopropanol are added, the reaction mixture is refluxed a short time, and the crystals of N-(5-nitro-2-furfurylidene)-3-amino-2-oxazolidone are filtered from the hot suspension. The product is washed with water and isopropanol and dried a yield of 23.3 grams, 92.8% based on N-(benzylidene)-3-amino-2-oxazolidone of MP 254° to 256°C is obtained, according to U.S. Patent 2,759,931. 

Another synthesis, described in detail in Scheme 12, was devised specifically for the introduction of deuterium at both ends of l-deoxy-D-t/ireo-pentulose.21,22 Stannylene methodology was used twice, first for glycol splitting with phenyliodonium diacetate, under strictly neutral conditions (necessary to preserve the benzylidene acetal), and secondly to convert the sequence -CHOH-CD3 to CO-CD3 by brominolysis. The final, labeled pentulose was l-deo y-D-threo-(1-2H3, 5-2H)pentulose. 

The ds-selechvity of the Diels-Alder reachon using aromahc aldehydes is demonstrated in the reachon of aldehydes such as 2-746, which contain a dienophile moiety. Treatment with N, N-dimethylbarbituric acid (2-747) in the presence of ethylene diammonium diacetate at 20 °C led to the ris-fused product 2-749 exclusively in 95% yield (Scheme 2.164) [377]. As an intermediate, the benzylidene-1,3-dicarbonyl compound ( )-2-748 is formed, which can be identified using online NMR-... 

The selective removal of one of two acetal groups that are symmetrically disposed within a diacetal may be achieved. l,3 2,4-Di-0-ben-zylidene derivatives of erythritol and L-threitol have been converted41 into their 1,3-acetals, and selective methanolysis of 2,3,2, 3 -tetra-0-benzoyl-4,6 4, 6 -di-0-benzylidene-a,a-trehalose gave42 the mono-benzylidene derivative in 47% yield, thereby offering a route to un-symmetrically substituted a,a-trehalose derivatives. 

Alternatively, when 21 was treated with benzaldehyde diethyl acetal-hydrochloric acid, ethyl 3,5 4,6-di-0-benzylidene-L-gulonate (76) was formed in >90% yield. Diacetal 76 was efficiently oxidized to 77 (>90% yield) with dimethyl sulfoxide-trifluoroacetic anhydride, or by way of the nitrate of 76 and triethylamine. Hydrolysis of 77 then afforded ethyl L-xy(o-2-hexulosonate in 86% yield.383... 

N-(Benzylidene)-3-amino-2-oxazolidone 5-Nitro-2-furaldehyde diacetate... 

Benzylidene and isopropylidene acetals are often used for the selective protection 1,2-cis or 1,3-cisjtrans diols of sugar derivatives. They are stable to strong basic conditions but quite fragile towards acid. Recently, dispirodiketal and cyclohexane-1,2-diacetal groups have been introduced to protect selectively 1,2-trans diols of carbohydrates. 

Benzylidene and isopropylidene acetals of irons-1,2-diols are very labile as a result of ring strain and are not often used for synthetic applications. Fortunately, the protection of these diols can be accomplished with the recently developed dispiroketal (dispoke)35 and cyclohexane-1,2-diacetal (CDA) groups.36... 

In 1942, Hann, Haskins and Hudson48 reported that the di-(o-nitro-benzylidene)-dulcitol described by Tanasescu and Macovski was not oxidized by lead tetraacetate and therefore could not possess the structure (1,2 5,6) arbitrarily assigned to it by the earlier workers. In view of the fact that the diacetal gave the known l,3,4,6-tetraacetyl-2,5-diben-zoyl-dulcitol when it was benzoylated in pyridine and then acetylated under acidic conditions, they regarded it as l,3 4,6-di-(o-nitrobenzyli-dene)-dulcitol, but of course this conclusion is not unequivocal. 

When the benzylidenation of sorbitol is carried out under slightly different conditions, a dibenzylidene-D-sorbitol (m. p. 219-221°, after purification via its dibenzoate) is obtained.29 116 Wolfe, Hann and Hudson29 demonstrated that oxidative scission of the diacetal resulted in the consumption of one molecular equivalent of lead tetraacetate and in the production of formaldehyde, together with a dibenzylidene-aldehydo-pentose, which yielded L-xylose when heated with aqueous... 

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