Benzoin, azidation

Figure 25-12 Isocratic HPLC separation of a mixture of aromatic compounds at 1.0 mL/min on a 0.46 x 25 cm Hypersil ODS column (C,8 on 5-jxm silica) at ambient temperature ( 22 C) (1) benzyl alcohol (2) phenol (3) 3, 4 -dimethoxyacetophenone (4) benzoin (5) ethyl benzoate (6) toluene (7) 2,6-dimethoxytoluene (8) o-methoxybiphenyl. Eluent consisted ot aqueous buffer (designated A) and acetonitrile (designated B). The notation 90% B in the first chromatogram means 10 vol% A and 90 vol% B. The buffer contained 25 mM KH2P04 plus 0.1 g/L sodium azide adjusted to pH 3.5 with HCI.

Reductions. VCI2 (also T1CI3) reduces benzils to benzoins (THF-H2O, 80-907o yield). Quinones are also reduced to hydroquinones (90-95 yield). Aryl azides are cleaved by VCI2 to arylamines and nitrogen (70-95% yield). ... 

Imidazolium salts, catalysts of the benzoin condensation 723 deuterium exchange in 705 Imines, from an azide and ethylene 725, 726 reduction of 68... 

Indium (III) bromide has been shown to catalyze the azidation of a-hydroxyketones with trimethylsilyl azide. The conversion is best done with strong electron-donating groups at the a-position. For example, benzoin (99) under the reaction conditions gives... 

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