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Dimethylketene 0-lactone dimer

DIMETHYLKETENE /3-LACTONE DIMER (3-Pentenoic acid, 3-hydroxy-2,2,4-trimethyl- /3-lactone)... [Pg.37]

In the presence of catalytic amounts of sodium methoxide, dimethylketene /3-lactone dimer is polymerized at moderate temperature to a polyester.3 At higher temperatures (above 100°), disproportionation to the cyclic trimer, hexamethyl-1.3,5-cyclohexanetrione, takes place.9 Addition of a stoichiometric amount of sodium methoxide to the lactone dimer generates the sodium enolate of methyl 2,2,4-trimethyl-3-oxovalerate. This reaction provides a convenient entry into certain ester anion chemistry that formerly required the use of a strong base like tritylsodium.10... [Pg.38]

Caution Dimethylketene -lactone dimer is a mild but deceptively persistent lachrymator. [Pg.72]

Enamines containing one -hydrogen atom react with the lactone dimer of dimethylketene to form aminocyclohexanediones 116). Polycondensation of acetone diethyl ketal takes place by treating it with morpholine and a catalytic amount of p-toluenesulfonic acid while distilling off the ethanol formed 117-119). The resulting spiran, bicyclo, and cyclooctadienone products differ from the known polycondensation products of acetone, and hence their formation probably involves enamine intermediates 119). [Pg.233]

The /3-lactone dimer of dimethylketene can be prepared by pyrolysis of its polyester, which is formed by the base-catalyzed polymerization of dimethylketene.3"6 In addition to the rearrangement of the normal dimer described above,6 the direct dimerization of dimethylketene in the presence of aluminum chloride3 or trialkyl phosphites7 leads to the /3-lactone dimer. [Pg.38]

The /3-lactone dimer of dimethylketene reacts with alcohols, phenols, mercaptans, and amines to form derivatives of 2,2,4-trimethylvaleric acid.3 In this respect it is a more powerful acylating reagent than the normal dimer, tetramethyl-l,3-cyclo-butanedione. The preparation of 2,2,4-trimethyl-3-oxovaler-anilide, for example, is accomplished easily with the lactone dimer, but is extremely difficult with the normal dimer.8... [Pg.38]

Although these reactions can be duplicated in most cases with the normal dimer of dimethylketene,11 the more reactive lactone dimer is the preferred reagent. The liquid form of this dimer is convenient to handle. A distinct difference in behavior of the dimethylketene dimers is noted when they are pyrolyzed. The normal dimer is dissociated at 600° to dimethylketene,12 but the lactone dimer is decarboxylated almost quantitatively at 450° to tetramethylallene.13... [Pg.38]

The reaction mixture is then cooled to 35-40° and poured into a stirred solution of 230 g. of sodium chloride and 6.0 g. of sodium acetate in 600 ml. of water at 40°. The mixture is stirred for 15 minutes and then is transferred to a separatory funnel the layers are separated, and the lower, aqueous layer is discarded. The crude product is distilled at reduced pressure through a stainless steel spinning-band column (Note 5). The yield of the /3-lactone dimer of dimethylketene is 122-132 g. (61-67%) b.p. 69-71.5° (14 mm.) (Note 6). The product may be redistilled and the fraction boiling at 119.5-120° (150 mm.), 20d 1.4380, collected. [Pg.124]

The lactone dimer of dimethylketene has been polymerized, a polyeater of the same struotuie... [Pg.105]

Oxaphospholans.—Full details have appeared of the reactions of the lactone and dione dimers of dimethylketen with a series of tervalent phosphorus esters and amides, and the postulated quinquecovalent intermediate (49) from the lactone dimer has been isolated in one case. Of potential mechanistic significance is the preferred migration of exocyclic substituents in the steps corresponding to (49) (50). [Pg.41]

The dimerization of dimethylketene usually produces the symmetrical dimer 7. However, the lactone dimer 8 can be generated from 7 by heating in DMF at 180 °C for 1 to 3 min... [Pg.245]

Disubstituted ketenes usually form the symmetric dimers. However, Staudinger and Klever also obtained a small amount of the j8-lactone dimers. This dimer is the only reaction product if the dimerization of dimethylketene is conducted in the presence of aluminum chloride as the catalyst Diphenylketene produces the -lactone dimer on addition of a catalytic amount of sodium methoxide . [Pg.246]

Very Htde is known about the toxicology of other dimeric ketenes. For the dimeric dimethylketene there is equivocal evidence of tumors resulting from massive exposure in rats reported for the P-lactone form (3,3-dimethyl-4-isopropyhdene-2-oxetanone), whereas the symmetric form (2,2,4,4 tetramethylcyclobutane-l,3-dione) induces tumors in mice after lengthy skin appHcations. [Pg.480]

The third type of cycloaddition results from the reaction of cyclopropanones with activated olefins. For example, dimethylketene adds to methyl substituted cyclopropanones affording the spiro lactones 153 a—c. 96,n8,i22b) Similarly the ortho ester 154 is formed from 1,1-dimethoxy-ethylene and 2,2-dimethylcyclopropanone 154 dimerizes to 155 upon standing. ng>... [Pg.149]

Ketenes are rarely isolated as they dimerise easily. Ketene itself 2 gives the lactone 5 but dimethylketene 6 gives the diketone 7. Other ketenes may give either type of dimer. Only a few ketenes, such as diphenyl ketene, are normally isolated. [Pg.251]

The dimerization of ketene leads to the formation of a lactone ( diketene ), the dimerization of dimethylketene furnishes a cyclobutanedione. In Figure 6.25, diketenes were introduced as reagents acylating alcohols to acetylacetates. [Pg.672]


See other pages where Dimethylketene 0-lactone dimer is mentioned: [Pg.124]    [Pg.124]    [Pg.73]    [Pg.1077]    [Pg.127]   
See also in sourсe #XX -- [ Pg.48 , Pg.72 ]




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