Hydro benzoin

A comparison of the H-bonding motif between supraminols 28 30, 29 30, and 29 32 suggests that the structure of the partner diol (e.g. cyclic diol versus acyclic diol) is an important factor in the control of the efficiency of the full or partial coordination in these supramolecular structures. Further insight into this aspect was obtained by the X-ray crystal analysis of heterochiral and homochiral complexes 29 33 and 29 34, formed between the diamine (R,R)-29 and (S, -hydro-benzoin (33) and (i ,7 )-hydrobenzoin (34), respectively [51]. After crystallization from benzene, the heterochiral complex 29 33 showed a higher melting... 

Besonders glatt erfolgt die saurekatalysierte Umlagerung von konstitutionell symmetri-schen di-sek.-Glykolen mitzwei Aryl-Resten zu Aldehyden (Hydro benzoin -Umlagerung)18. 

Benzaldehyde.—Kauffmann, by the electrolysis of benzaldehyde in a 12-15 solution of potassium bisulphide, obtained at the cathode a mixture of hydro-benzoin and iso-hydrobenzoln. According to his statements," an alcoholic solution of sodium hydroxide is more suitable for the reaction than the aqueous solution of bisulphide. Other aldehydes and ketones show a behavior similar to benzaldehyde. 

Benzo[c]furan-4,7-diones were probably synthesized for the first time by Pummerer and co-workers. Condensation of benzoin and hydro-... 

Recently, there has heen some work dealing with the cross-henzoin condensation to afford nonsymmetrical products chemoselectively. In this case, the Breslow intermediate has to he formed predominantly with only one of the aldehydes and react selectively with the other one. Kuhl and Glorius have succeeded in this area developing a selective hydro gmiethylation of aldehydes.With a different approach, it is also possible to use hindered ortho-substituted aldehydes to inhibit the retro-benzoin reaction and the attack of the As an extension, the cross-benzoin reaction has been... 

The benzoin condensation is the coupling of two aldehydes to afford ot-hydro>ycarbonyl compounds. In 1958, Breslow proposed the mechanism of the thiazolium-catalysed benzoin condensation reaction. It is believed that tetrahedral intermediate I is formed by nucleophilic attack of the in situ generated carbene A to the aldehyde. After proton transfer, intermediate II, now called the Breslow intermediate, is generated and reacts with an aldehyde to afford a new tetrahedral intermediate III. Elimination of the carbene catalyst affords the benzoin product and completes the catalytic cycle (Scheme 20.1). 

Polymeric insecticides containing benzoin- or ethyleneglycol carbamate via hydro-lysable or fight-sensitive spacer groups, or containing chlordimeform bound as a salt... 

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