Ketals enolethers

Monoene, Diene, Enamine, Enolether, Ketale, Acetale... 

The synthesis of the twistane-ketal 279 using endo-6-hydroxy-9-oxabicyclo[3.3.1]-nonan-2-one (274) or its acetate 227, resp., was nevertheless successful by applying the following route according to a procedure by Inhoffen etal. the keto-acetate 221 was treated with trimethyl orthoformate. From the reaction mixture which contained the dimethoxy-ketals 222 and 223 as well as the enolethers 224 and 225, the acetates 222 (63%) and 224 (5%) were isolated by chromatography. On base-hydrolysis they gave the alcohols 223 and 225. Pyrolysis of the ketal 222 and simultaneous distillation yielded 67% of the enolether 224. Finally by treating the dime-... 

Camphor sulfonic acid quinoline Enolethers from ketals... 

Enolethers from ketals with alkoxyl interchange... 

Gholestan-3-one ethylene ketal treated 5 min. at room temp, with acetic anhydride and BFg-etherate 2-acetyl-3-( -acetoxy)ethoxy-/d -cholestene. Y 78%. F. e., also from enolethers, s. R. D. Youssefyeh, Am. Soc. 85, 3901 (1963). 

A vigorous stream of HgS passed into 3-pentanone dimethyl (or diethyl) ketal and 2 parts of glacial acetic acid containing a little coned. H2SO4 and hydro-quinone until after 15-20 min. the theoretical amount has been absorbed pentane-3-thione. Y 80-85%. F. e., also from enolethers, s. R. Mayer and H.Berthold, B. 96, 3096 (1963). 

The complete ethanolysis of K CN in the presence of dry HCI gas and cone. H2SO4 furnishes triethyl [ C]orthoformate °. In normal synthetic organic chemistry triethyl orthoformate is used for the conversion of aldehydes and ketones into acetals, enolethers and ketals, respectively, as well as for the formylation of C- and Af-nucleophiles. In carbon-14 labeling the most frequent use has been for the preparation of purines and related compounds labeled at a methine position, through reaction of triethyl [ " C]orthoformate with appropriate substituted pyrimidine such as 131 (Figure 7.32), which reacts with the labeled reagent (in 10-25% excess) in the presence of catalytic amounts of a strong acid (p-TosOH, MsOH) under strictly... 

Orthoesters, like acetals and ketals, condense easily with enolethers in the presence of acid catalysts.— E Propenyl ethyl ether added during 1 hr. with stirring at 30° to ethyl orthoformate containing a little FeClg, stirring continued 1.5 hrs. at 45° l,l,3,3-tetraethoxy-2-methylpropane. Y 70%. F. e. s. I. N. Nazarov, S. M. Makin, and B. K. Kruptsov, 29, 3683 (1959) G. A. 54, 19462d. 

Phosphorus oxide chloride Enolethers from ketals Stereospecific dealcoholation... 

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