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Trimethylsilylketene reactions with

Trimethylsilylketene and acyl isocyanates generate 4-trimethylsiloxy-l,3-oxazin-6-ones 12 in situ, which smoothly react with the enamines of cycloalkanones to give bicyclic 2-pyridones 13 <96TL(37)4977>. The heterocycles 12 also undergo the Diels-Alder reaction with dimethyl acetylenedicarboxylate or methyl propiolate to furnish substituted 2-pyridones <96TL(37)4973>. [Pg.224]

Azomethine ylide cycloadditions have been utilized to prepare a number of novel fused pyrroles including pyrrolo[2,1 -a isoquinolincs <06CHJC279, 06TL1469> and pyrrolo[l,2-Zdpyridazines <06SL804>. Fused hydroxypyrroles were obtained in cycloaddition reactions with trimethylsilylketenes (TMS ketene) <06TL1469>. [Pg.141]

The reactions of the trimethylsilylketene 313 with silyl ketene acetals 314 provided /J,y-unsaturated esters 315 (equation 195) via a 1,5-silyl migration in the intermediate adduct 316461 462. [Pg.934]

Cycloaddition of trimethylsilylketene 108 with benzoylisocya-nate 282 was suggested to give 4-trimethylsilyloxy-l,3-oxazin-6-one 283. Interestingly, this six-membered heterocycle can be subjected to the Diels—Alder reaction with electron-deficient alkynes to afford 2-pyridone... [Pg.235]

Trimethylsilylketene reacts similarly with carbonyl isocyanates to give [4+2] cycloadducts, which undergo a Diels-Alder reaction with acetylenes or enamines to give 2-pyridones. A theoretical study of the reaction of silylketenes with carbonyl isocyanates and subsequent Diels-Alder reaction with ynamines was conducted recently. ... [Pg.300]

Trimethylsilylketene reacts smoothly with u./V-diarylnitrones to give oxoin-doles in good yields. On the other hand, the reaction of trimethylsilylketene with N-arylmethylnitrones gives a mixture of N,N-diacylamines and N-acylamines (Scheme 2.315) (836). [Pg.383]

More recently, Pirrung and co-workers established the facility with which the Rh2(OAc)4 catalyzed reaction of 2-diazocyclohexane-l,3-dione (306) and its substituted derivatives (Scheme 8.76) occurs with dihydrofuran and dihydropyran (351-353), vinyl acetates (354) (306 307), terminal alkynes (355) (306 308), methoxyallene (355), trimethylsilylketene (serving as a synthetic equivalent for ketene) (355), and heteroaromatic compounds (353). This reaction is quite useful... [Pg.605]

Reaction between trimethylsilyldiazomethane and trimethylsilylketene produces the disilylcyclopropanone. This was reacted with trimethylsilylazide to form the corresponding azetidinone in high yields after heating.122... [Pg.195]

Salicylaldehyde reacts with trimethylsilylketene dithioacetal in the presence of a Lewis acid to form the chroman 502, the product of a deoxygenative divinylation (Equation 208) <2001JOC3924>. This reaction can also be applied to salicylaldimines <2003JOC4947>. Treatment of 3,5-dibromosalicylaldehyde with methyl vinyl ketone (MVK) in the presence of DABCO leads to a chroman-4-ol as the major product <2002J(P1)1318>. A stereoselective one-pot synthesis of vy/z-fused chromans from salicylaldehydes, aromatic amines and cyclic enol ethers is carried out in the... [Pg.522]

The number of chiral diazaaluminolidine catalysts has been extended by Dymock, Kocienski and Pons, who introduced the more convenient to handle trimethylsilyl-ketene [31]. The catalysts in this study were prepared from slightly different sulfonamides but asymmetric induction was comparable with that obtained with the ketene and similar aldehydes. With trimethylsilylketene, two diastereomers are possible and in all examples studied the cis isomer 126 was the predominate product. TTie reactions in Table 7 were performed with 30 mol % catalyst—with 20 mol % catalyst the reaction is incomplete. A more active catalyst can be prepared from the bis-trifluoro-methylsulfonyl derivative of 128, but asymmetric induction was low. It was reported that ortho substituents on the aryl sulfonamide were necessary for higher induction but data were provided only for the aryl sulfonamide substituents summarized in Table 7. Both symmetrical and unsymmetrical diazaaluminolidines were examined as catalysts in an attempt to optimize asymmetric induction but significant differences were not found. The catalyst prepared from the symmetric bis-sulfonamide 128 with Ar = 2,4,6-tri-/yo-propylphenyl did not give any reaction even at 100 mol %. [Pg.299]

Elimination reactions. 1-Trimethylsilylethylbenzotriazoles deliver alkenes on exposure to CsF in DMF. In an oxidative homologation of aldehydes CsF effects the aldol condensation with 2-trimethylsilylketene 0,0-bistrimethylsilylacetal and the elimination step. [Pg.77]

A useful sabinene (767) synthesis has been described by Rousseau and Slougui. The keto ester 768 (R = O) was prepared conventionally from ethyl 4-methyl-3-oxopentanoate and converted to the methylene compound 768 (R = CH2) by a Wittig reaction. The trimethylsilylketene acetal 769 was then treated with bromoform and diethylzinc in pentane, yielding 70% of the ester 765 (R =... [Pg.402]

A stirred soln. of 4-benzyloxybutanal and trimethylsilylketene in methylene chloride treated at 0° with 0.1 M BFj-etherate in the same solvent until t.l.c. indicated completion of reaction, 2 drops of water added, the organic phase transferred by pipette onto anhydrous Na2S04, solvent replaced by acetonitrile, treated with finely crushed KF 2H2O, and stirred vigorously for 20 min at room temp, to complete desilylation - intermediate P-lactone (Y 81%), treated with 2 eqs. BF3-etherate in methylene chloride at —20° - product (Y 69%). Also tetrahydropyran deriv. s. K.T. Mead, B. Samuel, Tetrahedron Letters 29, 6573-6 (1988). [Pg.329]

Preparative Methods an advantage of f-butyl trimethylsilylacetate over its methyl and ethyl ester analogs is that it can be prepared by C-silylation of the lithium enolate of f-butyl acetate at —78 °C in THF (85-90% yield). Under the same conditions the enolates of methyl and ethyl acetate give primarily 0-silylated products. The reagent has also been prepared by a rapid boron trifluoride etherate catalyzed reaction of trimethylsilylketene with f-butyl alcohol. ... [Pg.147]

Preparation of Trimethylsilyl-Substituted Allenes. Treatment of (1) with a stabilized phosphorus ylide, (ethoxycarbonyl-methylene)triphenylphosphorane, affords the silyl substituted al-lenic ester in 85% yield (eq 9). These alkenation reactions only occur with stabilized phosphorus ylides unstabilized ylides reportedly form complex mixtures with trimethylsilylketene. [Pg.647]

The reaction of trimethylsilylketene with hexafluoroacetone similarly produces the four-membered ring [2+2] cycloadducts Similar [2+2] cycloadducts are obtained from trimethylsilylketene and BZOCH2CHO (90 %) and from benzylketene and Me3SiC=C-CHO(86%). [Pg.275]


See other pages where Trimethylsilylketene reactions with is mentioned: [Pg.255]    [Pg.822]    [Pg.52]    [Pg.275]    [Pg.352]    [Pg.514]    [Pg.421]    [Pg.1637]    [Pg.979]    [Pg.88]    [Pg.325]    [Pg.85]    [Pg.235]   
See also in sourсe #XX -- [ Pg.31 , Pg.118 ]

See also in sourсe #XX -- [ Pg.31 , Pg.118 ]




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Trimethylsilylketene

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