Ethers cleavage, with ring closur

Hydrogen bromide Cleavage of ethers with ring closure... 

A xanthone also results from the cyclization of 2 -nitro-6-hydroxy-2,4-dimethoxyben-zophenone, which is the sole product from a photo-Fries rearrangement of 3,5-dimethoxyphenyl 2-nitrobenzoate (81T209). Ring closure is effected in boiling piperidine and appears to involve elimination of nitrous acid together with ether cleavage. 

Therefore several reactions were subjected to various antibody catalyses, e. g., ester and enol ether cleavage, transesteiification, ketone reduction. Cope rearrangement, ring closure via epoxide opening, or Diels-Alder cycloaddition [74, 75]. An exceptional reaction is the antibody-catalyzed Robinson annulation of triketone 28 to the Wieland-Miescher ketone 29 on a preparative scale. Surprisingly, even the alkylation of diketone 27 with methyl vinyl ketone was catalyzed by the same antibody, but at moderate rates (Scheme 15) [76]. 

Salutaridinol 26, as drawn in Figure 5, contains the correct configuration for an allylic syn displacement to undergo ring closure and form thebaine. Thebaine, after enol ether cleavage, yields neopinone 27 which has been shown to exist in a chemical equilibrium with codeinone 28 in aqueous solution as well as under the conditions of plant metabolism.33 Codeinone NADP oxidoreductase in the presence of NADPH... 

Acetylenebenzofurans from cumulenehalides Activation of unsatd. halides by adsorption Ring closure with ether cleavage... 

C2-symmetric teraryls. The synthesis was accomplished by palladium-catalysed intramolecular coupling, with subsequent ester saponification, methyl ether cleavage and two-fold ring closure to give the expected bislactone (Scheme 5.52). ... 

Pyridine hydrochloride Ring closure with cleavage of ethers... 

N-Dealkylation, lactam ring closure with — 17, 898 O-Dealkylation (s. a. Ethers, cleavage)... 

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