Cope rearrangement potassium

E)-(Carboxyvinyl)trimethylam-monium betaine, 67 Ethyl 3,3-diethoxyacrylate, 131 Potassium hydride, 257 aza-Claisen rearrangement L-Valinol, 341 Cope rearrangement Ferric chloride, 133 oxy-Cope rearrangement Potassium hydride, 257 Silver(I) trifluoromethanesulfonate, 274... 

Oxyanionic Cope Rearrangement. Potassium bis(trimethyl-silyl)amide/18-crown-6 was shown to be a convenient alternative to potassium hydride for the generation of anions for oxyanionic Cope rearrangements (eq 23) ... 

In the synthesis of ( )-palominol and ( )-dolabellatrienone from famesol, Corey and Kania84 employed a dianion accelerated oxy-Cope rearrangement to form the 11,5-trans-fused ring system of the dolabellanes. Diol 112 was treated with potassium hydride in THF to afford a 1 1 mixture of products with iraws-ll,5-fused ring systems, 113 and... 

The estradiol derivative 588 was obtained in 91% yield via oxy-Cope rearrangement, which proceeded smoothly when the tertiary alcohol 587 was exposed to potassium hydride/18-crown-6 in THF at ambient temperature under an inert atmosphere... 

A formal synthesis of ( )-Eseroline (69) via a 3-aza-4-oxa-Cope rearrangement was reported. An iV-aryl A-hydroxycarbamate was reacted with 2-phenylsulfanylpropanoic acid to yield the O-acylhydroxamic acid derivative 65, R = H that rearranged in the presence of potassium bis(trimethylsilyl)amide. The [3,3] and [3,5] rearrangement products, respectively 66 and 67, were formed (equation 22). If the para-substituted hydroxamic acid 65, R = OCOBu-t is used, no [3,5] rearrangement product is observed and the [3,3] rearrangement product 68 is the only product formed (equation 23). The authors proposed two parallel mechanisms, a concerted pathway and an ionic mechanism by an ion-pair recombination. 

OXY-COPE REARRANGEMENT Grignard reagents. Potassium hydride. 

The use of a cationic aza-Cope rearrangement in concert with a Mannich cyclization has also been applied to the total synthesis of enantiomerically pure (—)-crinine (359) (205). In the event, nucleophilic opening of cyclopentenoxide with the aluminum amide that was formed on reaction of (/ )-a-methylbenzyl-amine and trimethylaluminum gave the amino alcohol 485 together with its (15,25) diastereomer. Although there was essentially no asymmetric induction in this process, the diastereomeric amino alcohols were readily separated by chromatography, and the overall procedure therefore constitutes an efficient means for the preparation of enantiomerically pure 2-amino alcohols from epoxides. When the hydrochloride salt derived from 485 was treated with paraformaldehyde and potassium cyanide, the amino nitrile 486 was formed. Subsequent Swem oxida-... 

The oxy-Cope rearrangement has also been used in synthesis of ( )-peripla-none-B (V/38), the sex excitant pheromone of the American cockroach (Peri-planeta americana) [24]. Scheme V/7 gives the preparation of the starting material, V/43, for the rearrangement step. The divinylcyclohexenol derivative, V/43, smoothly underwent an oxy-Cope rearrangement after conversion to its potassium salt. The reaction mixture was cooled to —78°, treated with (CH3)3SiCl and finally oxidized with m-chloroperbenzoic acid [24]. 

Some remarkable compounds can be made by this method. One of the strangest—a bridgehead alkene—was made by a potassium-alkoxide-accelerated Cope rearrangement in which a four-mem-bered ring was expanded into an eight-membered ring containing a trans double bond. 

OXY-COPE REARRANGEMENT Mercury(II) trifluoroacetate. Potassium hydride. Sil-ver(I) trifluoromethanesulfonate. 

Reaction of allylmagnesium bromide with enals (61a)-(61c) gave allylvinyl methanols (62a)-(62c) in good yields. Oxy-Cope rearrangement using potassium hydride gave 5-hexenals (63a)-(63c) in 60-70%... 

Potassium hydride and potassium hexamethyldisilazide are the most commonly used metal sources to generate the alkoxide . But recently, the indium(I)-mediated tandem carbonyl addition-oxy-Cope rearrangement of y-pentadienyl anions to cyclohexenones and conjugated aromatic ketones has been reported. For example, indium alkoxide 8.32, obtained after the addition of 5-bromopenta-1,3-diene (8.31) to the aromatic conjugated ketones 8.30, undergoes a spontaneous oxy-Cope rearrangement to give 8.33 in 55% yield (Scheme 8.9). 

Wender and cowoikers reported the first example of an enolate-accelerated Cope rearrangement in 1985. Exposure of the trienone (51 Scheme 4) to potassium hydride in THF at room temperature for 17 h led to the formation of a 1.2 1 mixture of (55) and (54) each rearranged trienone was produced as a mixture of alkene isomers. The facility with which the rearrangement of the ketone enolates takes place is underscored by the observation that the corresponding silyl enol ethers remain unchanged under identical conditions, and require temperatures in excess of 100 °C for efficient rearrangement. 

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