Benzoin acetates

Naphthyl acetate Benzoin acetate Phloroglucinol triacetate Hydroquinone diacetate Pyrogallol triacetate... 

Capillaries packed with poly-A-acryloyl-L-phenylalanine ethyl ester (Chiraspher) modified silica were used for electrochromatographic enantiomer separation of ben-droflumethiazide. To suppress bubble formation, the inlet buffer vial was pressurized to 12 bar and the outlet buffer vial to 4 bar [42], Acetonitrile or methanol were used as organic modifier whereby acetonitrile was superior to methanol. Non-aqueous p-CEC was performed on helical poly(diphenyl-2-pyridylmethylmethacrylate) coated on wide-pore aminopropyl silica [56]. With this chiral stationary phase, the enantiomer separation of Trogers base, benzoin acetate, methylbenzoin and trans-stilbene oxide was achieved by pressure-supported CEC, applying a higher pressure to the inlet than to the outlet buffer vial. 

Benzoin acetate, methylben-zoin, Troger s base, tra/w-stilbene oxide and 1,1 -binaphthyl-2,2 -diol Aminopropyl silica gel (LiChrospher 1000, 5 pm) coated with helically chiral poly(diphenyl-2-pyridylmethyl methacrylate) (PDPM) Methanolic solution of ammonium acetate (2.5 mM, pH 4.5) 300 mm x 100 pm i.d. 200 mm effective length, chiral separation 163... 

Another example of such complications are the differing photoreactions of para - and meta -methoxy benzoin acetates 194>. The ara-isomer undergoes predominately a-cleavage and a little cyclization, both apparently from the triplet. 

Benzoin acetate (5) and the keto diacetate (d) are the major products (according to gas chromatographic analysis) of oxidation of diphenylacetylene at a carbon anode and in acetic acid containing sodium acetate. The keto-diacetate is readily converted into benzil. Under these conditions acetate ion would be oxidized at <2-2 V (vs. 

Although very common with a-halocarbonyl compounds, cleavage of a-oxygenated substances by nu> cleophiles is almost unknown. A mixture of phenyl trimethylsilyl selenide (38) and MgBr2 dehalogenates substituted benzoin acetates under mild conditions. The reaction probably proceeds by the HSAB path (equation 11) the precise function of MgBr is unclear. 

Diarylquinoxalines are similarly prepared by reaction of o-phenylenediamine with benzils. The required benzils have been prepared traditionally by oxidation of the corresponding benzoins, which in turn have been prepared by treatment of the appropriate aldehydes with potassium cyanide. In a more recent procedure, benzils have been obtained in good yield by oxidation of para-substituted diphenyloxazoles with bromine in acetic acid. The oxazoles themselves are readily prepared by cyclization of the benzoin acetate with urea (Scheme 3). ... 

Ethanone, 1,2-diphenyl-2-(acetyloxy)- benzoin acetate 2601a ... 

The course of benzoin acetate photolysis in the presence of / - and y-CD in both solution and solid complexes is selective. Efficient caging for radical pair recombination induces a remarkable preference for the formation of a photocyclization product over type I products [283]. Similar cage effects improved selectivity for type II products in alkyldeoxybenzoin- -CD complexes in the solid state [284]. 

Replacement of hydrogen by acoxy groups s. 12, 218 13, 846 Benzoin acetates from desoxybenzoins s. 13, 225 H OAc... 

Photorearrangement of benzoin acetate 23 (Scheme 12) in the presence of fi- or y-CD highly favors the photocyclization product 24a over the recombination products 24b and 24c originating from the Norrish Type I cleavage [73]. 

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