Ketene diethylacetal

A small amount of the alcohol comes over at 51-52°/200 mm and then, after the heating bath is replaced, 4-6 cc. of an intermediate fraction distils. This is followed by a fraction which boils at 83-86°/200 mm. and which is collected as pure ketene acetal. A total of 78-87 g. is obtained (67-75 per cent of the theoretical amount). The major portion is collected while the temperature of the bath is 120-140°, and the remainder is obtained by raising the bath temperature to 170-180°. 

Ketene acetal is best stored in a bottle made of alkaline glass which is preferably new and dusted with sodium /erl.-butoxide (Note 7). The glass stopper should be very well greased. Even with these precautions a small amount of a voluminous precipitate of the white polymer will develop. 

The tert.-butyl alcohol is refluxed over quicklime, distilled, and then redistilled over 1 g. of potassium per 100 g. of the alcohol. Improved yields of ketene acetal are obtained from tert.-butyl alcohol that has been recovered from a previous preparation of the acetal. 

The potassium should be cut into pieces sufficiently small to pass through the neck of the flask. Sodium in tert.-butyl alcohol can be used, but it is necessary to carry out the subsequent reaction at 125° in sealed tubes. The amount of tert.-butyl alcohol specified is sufficient to provide for complete solution of the potassium as the ferf.-butoxide. 

An ebullator tube through which dry nitrogen was drawn has been used for the subsequent distillation under reduced pressure, but it is far more advantageous to use about six boiling-chips. Because of its rapid reaction with water, ketene acetal must be protected from moisture of the air. 

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Halogenopyrimidines react with active methylene groups, such as those in diethyl malonate, ethyl cyanoacetate, ketene diethylacetal, etc. For example, 4-chloro-6-methyl-5-nitropyrimidin-2-amine (454) and dimethyl sodiomalonate give dimethyl 2-amino-6-methyl-5-nitropyrimidin-4-ylmalonate (455) (63ZOB3132) 2-chloro-4,6-... 

Trichloro-s-triazine also reacts readily with carbon or phosphorus nucleophiles. Diethylmalonate anion forms a mono-derivative under mild conditions and the tri-substitution product (327) under vigorous conditions with excess nucleophile. Nucleophilic attack by the 7r-electrons of ketene diethylacetal to give 254 and of dimethylaniline to give 253 has been mentioned earlier. Two... 

Ketene diethylacetal, 23, 43 Ketene, diethyl ketal, 23, 43 Ketene dimer, 21, 4, 64 Ketene lamp, 21, 65 Keto acid, 20, 2... 

The transition metal-catalyzed cyclopropanation of alkenes is one of the most efficient methods for the preparation of cyclopropanes. In 1959 Dull and Abend reported [617] their finding that treatment of ketene diethylacetal with diazomethane in the presence of catalytic amounts of copper(I) bromide leads to the formation of cyclopropanone diethylacetal. The same year Wittig described the cyclopropanation of cyclohexene with diazomethane and zinc(II) iodide [494]. Since then many variations and improvements of this reaction have been reported. Today a large number of transition metal complexes are known which react with diazoalkanes or other carbene precursors to yield intermediates capable of cyclopropanating olefins (Figure 3.32). However, from the commonly used catalysts of this type (rhodium(II) or palladium(II) carboxylates, copper salts) no carbene complexes have yet been identified spectroscopically. 

The replacement of ring C by a cyclic anhydride ring could be looked upon either as elimination of ring C or replacement of the ring by a heterocyclic anhydride ring. In any case, Fields et al. showed that quinolizinium 2,3-dicarboxylic acid anhydride (37) underwent cycloaddition reactions with either cyclopentadiene or styrene to alFord the expected products (e.g., 38). The 2,3-dimethylquinolizinium ion did not undergo cycloaddition even with the more reactive ketene diethylacetal. 

Schollkopf and co-workers have synthesized a number of cyclopropanone acetals by the addition of various sulfur- and oxygen-containing carbenes to ketene diethylacetals (Table 3).26>27> Similarly, cyclopropanone dithioacetals may be prepared by the addition of the Ws-thiomethyl and Ws-thiobenzylcarbenes 12a, b to olefins.29) However, cyclopropanone acetal formation by this method requires double bonds with considerable electron enrichment and the yields are generally low. With unsubstituted olefins such as cyclohexene, the carbenes 12 a, b tend to form dimeric and trimeric products such as 13 and 14, instead of the double bond addition products. 

Functionalized enantiopure 5,6-dihydropyran-2-ones 917 are accessible from a Cu(n)- (BOX) catalyzed reaction of ketene diethylacetal 914 and a-dicarbonyl compounds 915 followed by hydrolysis of intermediate 916 with formic acid (Scheme 249, Table 42) <2000JA11543>. 

Schroder and co-workers studied the addition of formaldehyde-O-oxide, generated in situ at low temperature by ozonolysis of ketene diethylacetal, to the tropolonic ring of various colchicine analogues, Fig. (4) [80]. The intermediate ozonide E formed from 4 decomposed upon warming to give A-acetylcolchinol methyl ether 32 via the presumed intermediate F, in 81% yield. 

Lithiation of compound (570) (LAD) followed by reaction with carbonyl compounds yields the derivatives (571) (Equation (93)) <89AP(322)29l>. Diels-Alder reaction of compound (572) with ketene diethylacetal gave compound (573) (Equation (94)) <92CL485>. 

Isopren XIV/1, 377, 670 Keten-diethylacetal VII/4, 391 Lactame XI/2, 581 Maleinsaureimide IV/5b, 1502 Methoxy-ethen XIV/1, 935, 950 (2-Methoxy-ethyl)-vinyl-ether XIV/1, 941... 

Orthoesters react with hydrocyanic acid, catalyzed by ZnCh, to give 2,2-dialkoxycarbonitriles (424 equation 201)." These nitriles can also be obtained by treatment of orthoesters with acyl cyanides" or trimethylsilyl cyanide in the presence of Lewis acids (BF3, SnCh)." Cyanoselenation of ketene 0,0-acetals affords the nitriles (425 Scheme 77)," " from which other compounds of this type can be prepared, e.g. (426) and (427), by splitting off the phenylselenyl group. The acetonitrile derivative (428 equation 202) is a byproduct (23%) in the photochemical cycloaddition of ketene diethylacetal to 6-cyanouracil." ... 

McElvain and Kundiger used potassium t-butoxide in t-butanol for the conversion of bromoacetal into ketene diethylacetal. 

Where both donor and acceptor molecules are vinyl monomers then the generation of radical ions might be expected to polymerize both species. This appears to be so [see reaction (9)] when unsaturated ethers, such as / -dioxene, dihydropyran, ethyl vinyl ether, isopropyl vinyl ether, and ketene diethylacetal, are each mixed with vinylidene cyanide. Cycloadducts are also important... 

Kerosene, purified, 24, 7 Ketene, 21, 13, 64 Ketene diethylacetal, 23, 45 Ketene, diethyl ketal, 23, 45 Ketene dimer, 21, 4, 64 Ketene lamp, 21, 65 Keto acid, 20, 2 -Ketoglutaric acid, 26, 42 Ketone, 2-Fluorenyl methyl, 28,3,63 Ketone, methyl 9-phenanthryl, 28,6 Ketone, methyl 2-thienyl, 28,1 Knoevenagel condensation, 23, 60 24, 92 25, 42, 51 27, 24 28, 24 Kolbc synthesis of an alkyl a,a>-dicar-boxylatc, 21, 48... 

Conmarin has been studied extensively in this context in the absence of a sensitiser it gives a syn head-to-head dimer in the presence of benzophenone, as sensitiser, the anti isomer is formed the syn head-to-tail dimer is obtained by irradiation in acetic acid. Cyclobutane-containing products are obtained in modest yields by sensitiser-promoted cycloadditions of coumarins and 3-acyloxycoumarins with alkenes, ketene diethylacetal, and cyclopentene. ... 

Cyclobutane-containing products are obtained in modest yields by sensitiser-promoted cycloadditions to tetramethylethene, ketene diethylacetal and cyclopentene. ... 

Ketene acetals also undergo a facile [2-1-2] cycloaddition reaction with sulfenes. For example, a 79 % yield of 3,3-diethoxythietane 1,1-dioxide 17 is obtained in the reaction of ketene diethylacetal with sulfene. ... 

The unsaturated sulfene, generated from 1-propenesulfonyl chloride and triethylamine, reacts with ketene diethylacetal to give the [2+2] cycloadduct 18 and a [4+2] cycloadduct 19. 

Alkanesulfonyl chlorides with hydrogen atoms in the j8-position do not undergo cycloaddition reactions with ketene diethylacetal. Reaction of two equivalents of ketene diethylacetal with methanesulfonyl chloride in the absence of triethylamine affords a 5% yield of the [2+2+2] cycloadduct 20. ... 

Ketene-0,0-, N,N-, N,0-, N,S- and 5,5-acetals react readily with alkyl, aryl and especially arenesulfonyl isocyanates to give 1 1 adducts. The structure of the adducts depends on the degree of substitution on the jS-carbon atom. The /3-disubstituted ketene acetals give [2+2] cycloadducts In the reaction of phenyl isocyanate with ketene diethylacetal, a six-membered ring 2 1 cycloadduct is obtained and mixtures of the [2+2] and the [2+2+2] are obtained from substituted keten 0,0-acetals Heterocyclic e-caprolactim ethers 92, which are in equilibrium with ketene OW-acetals, react with aryl isocyanates at room temperature to give [2+2] cycloadducts 93 and at 150 °C to produce [2+2+2] cycloadducts 94. ... 

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