Benzaldehyde dimethylacetal

Carbocations can also be generated during the electrolysis, and they give rise to alcohols and alkenes. The carbocations are presumably formed by an oxidation of the radical at the electrode before it reacts or diffuses into solution. For example, an investigation of the electrolysis of phenylacetic acid in methanol has led to the identification of benzyl methyl ether (30%), toluene (1%), benzaldehyde dimethylacetal (1%), methyl phenylacetate (6%), and benzyl alcohol (5%), in addition to the coupling product bibenzyl (26%). ... 

A mixture of TMSOTf (0.1 mmol, lmol%), allyltrimethylsilane (11.5 mmol) and dichioromethane (1 ml) was cooled to -78 °C, and to this was added benzaldehyde dimethylacetal (10.5 mmol) in dichioromethane (4ml). The resulting mixture was stirred for 6h at —78°C, and then poured into saturated sodium hydrogen carbonate solution (10 ml) and extracted with ether (3 x 20 ml). The combined organic extracts were washed with brine, dried and concentrated. Chromatography on silica gel (1 20 ether hexane) gave 4-pheny]-4-methoxybut-l-ene (9.2mmol, 88%). 

Polymer-attached 1,3-diols react with substituted benzaldehyde dimethylacetals in the presence of MesSiCl 14 to give 1,3-dioxanes in high yields [30]. 

It has been proposed that there may be a single electron transfer mechanism for the Mukaiyama reaction under certain conditions.72 For example, photolysis of benzaldehyde dimethylacetal and 1-trimethylsilyloxycyclohexene in the presence of a... 

Technically interesting are the indirect electrochemical oxidations of benzylic alcohols (Table 11, No. 15-18) benzaldehyde dimethylacetals (Table 11, No. 19) and alkyl aromatic compounds (Table 11, No. 20, 21) It could be proven that benzylic alcohols are oxidizable using tris(2,4-dibromophenyl)amine as mediator not only in acetonitrile in a divided cell but also in methanol in an undivided cell... 

Step 6 Acid-catalyzed /rmembered ring acetal. 

Benzaldehyde dimethylacetal (200 pi, 1.33 mmol) and a catalytic amount of p-toluenesulfonic acid (37 mg) are added to methyl (2R,3S)-3-(4-nitrobenzenesulfonamido)-3-phenyl-2-hydroxypropionate (315 mg, 0.83 mmol) in toluene 5 ml. The mixture is heated at 100°C under reduced pressure (15 mm mercury) with no condenser. After 1 h the crude reaction mixture is diluted with ethyl acetate and washed with water (2 times). After drying the organic layer over magnesium sulfate the crude material is purified by column chormatography (silica gel eluting with ethyl acetate/cyclohexane, 35/65) to give the (2S,4S,5R)-2,4-diphenyl-3-(4-nitrobenzenesulfonamido)-5-methoxycarbonyl-l,3-oxazolidine, melting point 118°-120°C. 

A pair-selective aldol reaction proved to be possible and is illustrated in Eq. (25) from the four starting materials, only two products were obtained [100], This clearly indicates that the coupling of the ketene silyl acetal and acetophenone and that of the enol silyl ether and benzaldehyde dimethylacetal are very favorable paths, whereas the reactions of other combinations are not. A similar phenomenon is illustrated by Eq. (26) [100]. 

Alternatively, compound 54 was converted to the corresponding benzylidene acetal, upon reaction with benzaldehyde dimethylacetal, whose dithioacetal was hydrolyzed to give 58, which was reacted with nitromethane to afford 59 in 83% yield and >99 1 diastereose-lectivity. Treatment of 59 with ethanethiol and stannous chloride effected removal of the benzylidene acetal, without dehydration of the 3-hydroxynitro functionality, to afford the corresponding triol in 82% yield. Protection of the triol with excess TBSOTf afforded a 91% yield of the corresponding TBS ether. Selective removal of the phenolic TBS group was effected by treatment with CSA in methanol to afford 56 in 88% yield, which upon similar sequence of reactions as shown above afforded 60 as the sole cyclization product in 90% yield. 

One of the early synthetic objectives in our route was the synthesis of aziridine 44 in copious amounts. Happily, we were able to prepare this compound fairly readily on large scale (0.5 kg) using a slightly modified version of the Hough and Richardson five-step procedure that was first published in Carbohydrate Research in 1965 (Scheme 9). In their route to 44, the cheap and readily available monosaccharide, D-glucosamine hydrochloride, is chemoselectively A-acylated with benzoic anhydride in methanolic sodium methoxide to obtain 46, and a Fischer glycosidation is then performed to access the a-methylpyranoside 47. An O-benzylidenation is subsequently implemented on 48 with benzaldehyde and zinc chloride (although in our case we preferred to use benzaldehyde dimethylacetal and a catalytic amount of p-toluenesulfonic acid in DMF at 55 °C for this purpose). 

Benzylidene acetals are generally prepared following two standard procedures that is, by reacting a dihydroxy compound (i) with benzaldehyde in tetrahydrofuran in the presence of stoichiometric amounts of Lewis acid and (ii) with benzaldehyde dimethylacetal in dime-thylformamide in the presence of a catalytic amount of PTSA [39]. 

With regard to the preparation of benzylidene acetals, there are two major drawbacks. Whenever possible, both the 1,2 and the 1,3 acetals are formed, leading to a mixture of products Furthermore, the equilibrium of acetal formation is disfavored by the water produced in the reaction. These disadvantages are largely overcome by reacting benzaldehyde dimethy-lacetal in tetrahydrofuran in the presence of stoichiometric amounts of zinc chloride-diethy-lether complex the use of benzaldehyde dimethylacetal instead of benzaldehyde itself favors the formation of 1,3-dioxanes and facilitates the purification of final products, while the use of zinc chloride-diethylether complex instead of PTSA avoids the presence of added water in the reaction medium, increasing the yield of the desired products. 

In contrast to the acetalization of 370 with acetone, which favors the 5-membered acetonide 437 over the 6-membered acetonide 338 (9 1), acetalization of 370 with benzaldehyde in the presence of trifluoroacetic acid [164] or transacetalization with benzaldehyde dimethylacetal [102,165,166] produces only the 6-membered acetal 754. This phenomenon makes it possible for the chemist to conduct operations at the C-1 hydroxyl of 370. 

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]. 

The reaction of 151 with benzaldehyde dimethylacetal 157 proceeds in a similar fashion < 1999TL3727,2000S1170>. The resulting azomethine imine intermediate 158 reacts with the dipolarophilic diethyl acetylenedicarboxylate to give 159. When kept as an oil, the latter is oxidized rapidly in the presence of air to give pyrazole 160 (Scheme 23). 

A detailed comparative study on the benzylidenation of D-arabinose diethyl-dithioacetal with benzaldehyde dimethylacetal and catalytic TsOH or with benzaldehyde in the presence of HCl or ZnCb has been published, and the benzylidenation of methyl a-D-mannopyranoside with benzaldehyde and TsOH has been improved, with yields of acetal 9 >72%." Transacetalation of fully 6-0-pivaloylated a-, P-, and y-cyclodextrins with benzaldehyde dimethylacetal and catalytic camphorsulfonic acid gave mono-benzylidene products 10. Reductive ring-opening (LAH/AIQ3) of compounds 10 afforded predominantly the 2 -0-unprotected derivatives 11. ... 

The potential benefits of using these clay catalysts together are highlighted by the development of a new one-pot sequential synthesis of epoxynitrile (Scheme 6.24) [134]. The reaction of methanol, cyanoace tic acid, benzaldehyde dimethylacetal, and hydrogen peroxide in the presence of the Ti +-mont and HT afforded epoxynitrile in 91% yield. The four reactions, esterification (by acid), deacetalization (by acid), aldol reaction (by base), and epoxidation (by base) [11, 135], proceeded in a single reactor. 

The main product of reaction between D-ribono-y-lactone and benzaldehyde dimethylacetal is the 2,3-acetal and not the 2, -acetal of the 6-lactone as previously proposed.Long chain aliphatic amines (Cg-C g) have been condensed with D-gluconic acid lactone to give amphlpathic products which form gels at low concentrations in aqueous solution. The morphology of the gels has been Investigated by electron microscopy. 

Electrophile = acrolein, methyl acrylate, acrylonitrile, 2-cyclopentene-1 -one, benzaldehyde dimethylacetal, 2,2-dimethoxypropane, 2-cyclohexene-1-one or dimethylfurmarate... 

In the second approach, treatment of lactoside derivatives 19 and 63 with benzaldehyde dimethylacetal in dry acetonitrile using p-toluenesulfonic acid as catalyst gave the 4, 6 -0-benzylidene derivatives 66 and 67 in 93% and 89% yield, respectively. Further derivatization of 23 (Scheme 4) was also considered in order to prepare sialyl Le as shown in Scheme 15. The disarmed-latent trisaccharide acceptor 23 was first coupled with ethylthio fucopyranosyl donor 57 in the presence of NIS/TfOH in dichloromethane at —70°C to give sialylated tetrasaccharide 70 in 63% yield together with recovered trisaccharide acceptor 23 (17%) and a minor unidentified regioisomer (less than 10%) (Scheme 15). 

Write an equation for the reaction of benzaldehyde dimethylacetal with aqueous acid. 

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