4,4 -Dimethoxybenzoin

A solution of freshly distilled anisaldehyde (150 g., 1.10 moles) (p. 129) in 200 ml. of ethanol is mixed with a solution of 30 g. of potassium cyanide (free from cyanate) in 120 ml. of water, and the resulting mixture is heated under vigorous reflux for 2 hours. An additional 30 g. of potassium cyanide is added, and reflux is continued for another 2-hour period. After cooling, the upper layer solidifies upon seeding with a crystal of the product, and the solid is removed by filtration. The filtrate is heated under reflux for another 2-hour period with a third portion of 30 g. of potassium cyanide, and this yields an additional quantity of 4,4 -dimethoxybenzoin. The combined crude product is recrystallized from ethanol to give 110 g. (73%) of product melting at 113°. 

CAS 119-52-8 El NECS/ELINCS 204-330-8 Synonyms p-Anisoin 4,4 -Dimethoxybenzoin Ethanone, 2-hydroxy-1,2-bis(4-methoxyphenyl)- 2-Hydroxy-1,2-bis (4-methoxyphenylj-ethanone Classification Aromatic ketone Empirical C16H16O4... 

Dimethoxybenzidine. See Dianisidine 3,3 -Dimethoxybenzidine-4,4 -diisocyanate. See Dianisidine diisocyanate 4,4 -Dimethoxybenzoin. See Anisoin 3,3 -Dimethoxy-1,r-biphenyl-4,4 -diamine. See Dianisidine... 

The dehydrogenation of acyloins to 1,2-dicarbonyl compounds catalyzed by [CuClpy] in non-protic solvents like nitrobenzene, dichloromethane and DMSO has been reported [55]. Model substrates were benzoin, pyridoin, 4,4 -dimethoxybenzoin, furoin and acetoin. The rate law for benzoin (B) oxidation in nitrobenzene is ... 

Mo 02(S2CNEt2)2] were used as catalysts in a comparative study of the oxidation of benzoin, 4,4 -dimethoxybenzoin and 4,4 -dichlorobenzoin in... 

Under Mukaiyama s conditions aromatic a-hydroxyketones (benzoin, 4,4 -dimethylbenzoin and 4,4 -dimethoxybenzoin [anisoin]) are readily oxidized by dioxygen at room temperature in the presence of excess aldehyde or aldoacetal with catalytic amounts of Co(acac)2 or Fe(acac)3 under homogeneous conditions . The stoichiometric equation is shown in Figure 55. 

Photolysis, 350 nm, CH3CN, H2O. The by-product from the reaction is 2-phenyl-benzo[ ]furan. Cleavage with TBAF and PhCH2SH has been demonstrated (70-94% yield). The related 3,5-dimethoxybenzoin analogue is cleaved with a rate constant of >10 sec Photolytic cleavage occurs by heterolytic bond dissociation. ... 

Phenyl(o-nitrophenyl)methyl, 545 2-(2-Nitrophenyl)ethyl, 545 6-Nitroveratryl, 545 4-Methoxyphenacyl, 545 3, 5 -Dimethoxybenzoin, 546... 

This group is stable to 50% TFA/CH2CI2, NaOH, and 20% piperidine/DMF. 11. 3, 5 -Dimethoxybenzoin Carbamate (DMBOCONR2)... 

The DMB carbamate can also be introduced through the 4-nitrophenyl carbonate. " It has been prepared from an isocyanate and 3, 5 -dimethoxybenzoin. The synthesis of a number of other substituted benzoins as possible protective groups has been described. ... 

Using only benzaldehyde as substrate (see Fig. 3.1.8a), (R)-benzoin can be obtained on a 200 mg scale from a 40 mb two-phase system. This corresponds to a volumetric productivity of 53 g L d for the organic phase, or 20 g d with respect to the overall reaction volume. When using 2-chlorobenzaldehyde and 3-methoxybenzaldehyde as substrate in equimolar amounts, (R)-2-chloro-3 -methoxybenzoin is formed as the main product with approximately 80% selectivity (see Fig. 3.1.8b). The symmetric benzoins (2,2 -dichlorobenzoin, 3,3 -dimethoxybenzoin) are formed as side-products. The main product is obtained on a 150 mg scale, which corresponds to a volumetric productivity of 40 g L d with regard to the organic phase. 

Importantly, TV-carbamoyl derivatives of primary amines obtained from photolabile benzoins exist in varying proportions as cyclic hydroxyoxazolidinone tautomers. Therefore, the preparation of TV-carbamoyl derivatives of benzoins is applicable only for secondary amines and TV-alkylated amino acids. 244 At basic pH unsymmetrical benzoins, such as 3,5-dimethoxybenzoin, their mixed carbonate and carbamate derivatives, tend to equilibrate to the isomeric forms. Nevertheless, in TFA and aqueous solutions at pH 8 the structural integrity is fully maintained. 244 Preparation of 3,5-dimethoxybenzoin-derived carbamates of secondary amines and amino acids can be mediated by either CDI/methyl triflate in ni-tromethane 246 or 4-nitrophenyl chloroformate/DMAP in dry THF. 244 ... 

Fig. i Matrix isolation method of surface immobilization of probe oligonucleotide/poly-electrolyte mixed film for enhanced selectivity. Phase 1 Photolabile dimethoxybenzoin (DMB) protecting groups are selectively exposed to electromagnetic radiation of appropriate wavelength to provide reactive sites in which polyelectrolyte spacers can be immobilized. Phase 2 The remaining DMB-protected sites are photo-deprotected to expose sites for probe oligonucleotide immobilization onto the solid surface... 

A few years later, Sheets suggested that co-oxidation of the biimidazole derived from 2-chloro-3, 4 -dimethoxybenzoin and o-chlorobenzaldehyde and 2-(o-chlorophenyl)-4,5-diphenylimidazole would give a still less expensive photo-oxidant (Scheme 4.13) with less visible sensitivity, thus making for better photofixing. 

Pirrung, M.C. and Shuey, S.W. (1994) Photoremovable protecting groups for phosphorylation of chiral alcohols. Asymmetric synthesis of phosphotriesters of (—)-3, 5 -dimethoxybenzoin. Journal of Organic Chemistry, 59, 3890-3897. 

Shi, Y Corrie, J.E.T. and Wan, P. (1997) Mechanism of 3, 5 -dimethoxybenzoin ester photochemistry heterolytic cleavage intramolecularly assisted by the dimefhoxybenzene ring is the primary photochemical step. Journal of Organic Chemistry, 62, 8278-8279. 

Pirrung, M.C. and Huang, F C.-Y.D (1995) Photochemical deprotection of 3, 5 -dimethoxybenzoin (DMB) carbamates derived from secondary amines. Tetrahedron Letters, 36, 5883—5884. 

This principle has been extended in various directions, e.g., for carrying out a photochemical solid phase synthesis in microchip format based on the used of the dimethoxybenzoin moiety [303]. 

Givens58 and Pirrung59 used photolabile 3 3 -dimethoxybenzoin esters for the protection of phosphotriesters. A complication attending the use of racemic 3 5 dimethoxybenzoin is the generation of four diastereoisomers if the phosphate is chiral. An asymmetric synthesis of 3, 5 -dimethoxybenzoin 303 [Scheme 7.30] via the 0-trimethylsilyl-3,5-dimethoxybenzaldehyde cyanohydrin 303 minimises the number of diastereoisomers created in the phosphorylation of chiral alcohols. Thus reaction of 303 with 2 - cyanoethoxy)(NPNf-diisopropy amino)-chlorophosphine afforded the phosphoramidite 30.4 which then reacted with Boc-Ser-OMe to give the two diastereoisomeric phosphotriesters 303, Photode-... 

Scheme 13 Photocyclization of Dimethoxybenzoin Carbamate Derivatives and Structure of the Inert Cyclic Carbamate...

The dimethoxybenzoin group has an advantage over the c-nitrobenzyl group because it produces a nonreactive benzofuran upon photolysis, whereas the... 

Disubstituted-6-nitrobenzyl, 767 Phenyl(o-nitrophenyl)methyl, 767 2-Nitrophenylethyl, 767 6-Nitroveratryl, 768 4-Methoxyphenacyl, 768 3 ,5 -Dimethoxybenzoin, 768 9-Xanthenylmethyl, 768 W-Methyl-W-(o-nitrophenyl), 768 W-(2-Acetoxyethyl) amine, 769... 

Dimethoxybenzoin Derivative, 980 4-Hydroxyphenacyl, 981 4-Methoxyphenacyl, 981 l-(2-Nitrophenyl)ethyl, 981 o-Nitrobenzyl, 981... 

---