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Wittig rearrangements reaction

Rase-catalyzed elimination reactions and Wittig rearrangement reactions are probably also important under these experimental conditions (7). [Pg.216]

Reminder of the conversion to allylic sulfoxides The [2,3] Wittig rearrangement Reactions with Electrophiles... [Pg.339]

A domino addition-Wittig-rearrangement reaction was described that started with the addition of an a-hydroxy ester derivative on the 2,3-unsaturation of (triphenyl-phosphoranylidene)ketene, followed by an intramolecular Wittig olefination of the primarily formed adduct. Under MW irradiation, the furanone derivative so formed underwent rearrangement of its side chain and finally the newly formed 2-butenyl substituent was saturated by catalytic hydrogenation (Scheme 93). ... [Pg.103]

The aza-[2,3]-Wittig rearrangement of a vinylaziridine-derived quaternary azir-idinium ylide (i.e., [2,3]-Stevens rearrangement) has recently been reported (Scheme 2.53) [86], The aziridinium ylide 219, generated by the intramolecular reaction of a copper carbenoid tethered to a vinylaziridine, underwent a [2,3]-Ste-vens rearrangement to furnish the bicydic amine 220 with the indolizidine skeleton. [Pg.62]

Of these reactions, the [2,3] Wittig rearrangement in particular has often been used as a means of transferring chirality. The product of this reaction has potential chiral centers at C-3 and C-4 (if R ), and if the starting... [Pg.1454]

Sigmatropic rearrangements of anions of (V-allyl amines have also been observed and are known as aza-Wittig rearrangements.291 The reaction requires anion stabilizing substituents and is favored by (V-benzyl and by silyl or sulfenyl substituents... [Pg.588]

A Michaelis-Arbusov rearrangement followed by a Wittig-Horner reaction is involved in preparation of the distyrylbenzene derivative 11.37, as shown in Scheme 11.15. Precautions must be taken in the first stage to minimise formation of the carcinogenic by-product bis(chloromethyl) ether 11.16. The stilbene bis-ester 11.38 can be made by a similar procedure, or alternatively by the reaction of ethyl acrylate with 4,4 -dibromostilbene in the presence of a palladium-based catalyst (Scheme 11.16), a synthesis that yields the required trans form of the brightener. [Pg.332]

An earlier example of this type of domino reaction was reported by Greeves and coworkers (Scheme 2.194) [443]. Treatment of either the ( )- or (Z)- allyl vinyl ether 2-870 with NaH initiates the [2,3]-Wittig rearrangement to afford 2-872 via 2-871. The subsequent oxy-Cope rearrangement led to the aldehyde 2-873, which was reduced with NaBH4 to give the alcohols 2-874. Both isomers of 2-870 predominantly generated the (/ )-xyu-product 2-874 in comparable ratios as the main product. [Pg.183]

A combination of a Claisen rearrangement, a Wittig rearrangement and a Wittig reaction was described by Mali and coworkers for the synthesis of 6-prenylcou-marins. In these transformations, 2-prenyloxybenzaldehydes was employed as substrate [105]. [Pg.325]

The aza-[2,3] Wittig rearrangement of aziridines is an excellent method for the synthesis of substituted piperidines. The analogous reaction of an epoxide has recently been examined <06TL7281>. Reaction of divinyl epoxide 48 with /-butyl diazo acetate provides the ylide intermediate 49, which then undergoes the [2,3] Wittig rearrangement to 50, Several catalysts were examined as catalysts for the formation of 49. It is noteworthy that the copper catalyst performed much better than the more widely used rhodium catalysts. [Pg.79]

The application of RCM to dihydropyran synthesis includes a route to 2,2-disubstituted derivatives from a-hydroxycarboxylic acids. In a one-pot reaction, the hydroxy esters undergo sequential O-allylation, a Wittig rearrangement and a second O-allylation to form allyl homoallyl ethers 8. A single RCM then yields the 3,6-dihydro-2//-pyran 9. The process is readily adapted not only to variably substituted dihydropyrans but also to 2-dihydrofuranyl and 2-tetrahydrooxepinyl derivatives and to spirocycles e.g. 10 through a double RCM (Scheme 4) <00JCS(P1)2916>. [Pg.318]

Fig. 34 Approach to higher carbon sugars via the Wittig-type reaction Unusual rearrangement of the enone induced by triflate leaving group. [Pg.243]


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See also in sourсe #XX -- [ Pg.216 ]




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WITTIG Rearrangement

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