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Allenes, carbonylation

Reductive Cyclization of Acetylenic and Allenic Carbonyl Compounds 524... [Pg.493]

A single example of the reductive cyclization of allenic carbonyl compounds is reported, which employs a rhodium-based catalyst in conjunction with Et3SiH as terminal reductant.113 This protocol promotes hydrosilylation-cyclization to form both five- and six-membered rings with exceptional levels of yy -diastereocontrol. As revealed... [Pg.527]

Although detailed mechanistic studies are not reported, the postulated mechanism for the reductive cyclization of allenic carbonyl compounds involves entry into the catalytic cycle via silane oxidative addition. Allene silylrhodation then provides the cr-allylrhodium hydride A-18, which upon carbometallation of the appendant aldehyde gives rise to rhodium alkoxide B-14. Oxygen-hydrogen reductive elimination furnishes the hydrosilylation-cyclization product... [Pg.528]

Propargyl alcohols also react with the ether of an enol of carbonyls and lactones to give allenic carbonyl compounds [79a-d] (Eq. 58). [Pg.22]

Unsaturated carbonyl compounds (see also Acetylenic carbonyl compounds, Allenic carbonyl compounds) Unsaturated acids a,P-Unsaturated acids Sodium chlorite, 280 7,8-Unsaturated acids L-Valinol, 341... [Pg.397]

Allenic Alder-ene reactions, characteristics, 10, 584 Allenic carbonyl compounds reductive cyclization, 10, 524 silver-catalyzed cycloisomerizations, 9, 559 Allenic carboxylic acids, silver-catalyzed cycloisomerizations, 9, 559... [Pg.49]

Silver-catalyzed cyclization reactions of allenic carbonyl compounds were applied for the total synthesis of various natural products, including rubifolide,331 kallolide A and B,332,332a and deoxypukalide.333 In their total synthesis of the enantiomer of rubifolide 396, Marshall and Sehon331 took advantage of the silver-catalyzed cycloisomerization of the allenic ketone 393 to the furan 394, as well as of the analogous reaction of the allenic carboxylate 395 to the target molecule 396 (Scheme 115). [Pg.559]

If X in Scheme 41 represents a cyanide group (X = CN) the rearrangement of the anion leads to a cyanohydrin anion as the product, which can yield a carbonyl function directly.The reaction is not only known for allylic ethers but also for propargylic ethers, giving access to allenic carbonyl compounds in the latter case (equation 39). ... [Pg.852]

Allenes Carbonyl compounds are converted to allenes on reaction with alkenyltitanocenes (16 examples, 40-89%). [Pg.4]

Prior hydrolysis of the difluoromethylene group in either the 3- or 17-cycIo-propenyl alcohols (13Sa and b) affords the corresponding cyclopropenones, which on treatment with the fluoramine reagent are converted cleanly into analogous 3 - and 17/9-allenic carbonyl fluorides (142) and (143) in this case a-isomers were not detected (Scheme 38). [Pg.99]

The formal [2+2+1] cocyclization of alkenes, alkynes and CO by transition metal complexes has been used as a powerM tool for the synthesis of cyclopentenones (Scheme 10.1a) [15]. Other variants of C=C bond like allene, carbonyl or imino moiety can also be used in place of alkene or as a partner of alkene to synthesize 4-or 5-alkylidene cyclopentenones, [16] y-lactones [17] or y-lactams, [18] respectively. Catalytic [2+2+1] cocyclization can also be used with full efficiency to construct heterocyclic compounds using het-erocumulenic compounds such as carbodiimides and/or isocyanates with alkynes and CO (Scheme 10.1c). [Pg.355]

As one of the pioneering works concerning allene carbonylation, Alper et al. report palladium-catalyzed alkoxy-alkoxycarbonylation of allenes with carbon monoxide and methanol in the presence of CUCI2/HCI/O2 (Scheme 11.1) [3]. [Pg.291]

Clinet, j. C., and G. Linstrumelle An efficient method for preparation of conjugated allenic carbonyl compounds. The synthesis of two bark beetle pheromones. Nouveau J. Chim. 1, 373—374 (1977). [Pg.163]


See other pages where Allenes, carbonylation is mentioned: [Pg.1006]    [Pg.117]    [Pg.382]    [Pg.166]    [Pg.271]    [Pg.167]    [Pg.167]    [Pg.39]    [Pg.296]   
See also in sourсe #XX -- [ Pg.965 ]




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