Diethyl keten

For this reason, a reinvestigation of the cyclic ketene acetal, 2-methylene-l,3-dioxolane (I), that had been prepared by McElvain and Curry (14) was undertaken. Although McElvain and Beyerstedt (15) reported that benzoyl peroxide had no appreciable effect on diethyl ketene acetal, no such study was reported (14) for the 2-methylene-l,3-dioxolane (I). The synthesis was carried out as follows (6) ... 

Since the diethyl ketene acetal (XII) appears to be a moderately effective chain transfer agent as well as a comonomer, a search... 

Whereas 260 does not react with electron-rich dipolarophiles, the more delocalized isomiinchnone 261 does react with both electron-rich and -deficient dipolarophiles (154). A detailed FMO analysis is consistent with these observations and with the regiochemistry exhibited by diethyl ketene acetal and methyl vinyl ketone as shown in Scheme 10.36. The reaction of 261 with the ketene acetal to give 262 is LUMO-dipole HOMO-dipolarophile controlled (so-called lype III process). In contrast, the reaction of 261 with methyl vinyl ketone to give 263 is HOMO-dipole LUMO-dipolarophile controlled (so-called lype I process). In competition experiments using a mixture of A-phenylmaleimide and ketene acetal only a cycloadduct from the former was isolated. This result is consistent with a smaller energy gap for... 

The treatment of bis(trimethylsilanyl)methanesulfonyl chloride with triethylamine led to the formation of a sulfene 89, which upon reaction with diethyl ketene acetal gave a thietane adduct 90. The latter led to thiete 1,1-dioxide 91 in very poor yield (5%) after the loss of trimethylsilyl ethoxide (Equation 29) <2000CJC1642>. 

The first example of a bimolecular 1,3-dipolar cycloaddition between an isomtinchnone and an electron-rich dipolarophile was reported by our group several years ago [27]. The reaction of diethyl ketene acetal and isomtinchnone 9 gave cycloadduct 29 in high yield. Again, only one regioisomer was obtained and the regiochemistry encountered is consistent with cycloaddition involving the HOMO of diethyl ketene acetal and the LUMO of isomunchnone 12 (n = 1). 

Thus, upon CIR of electron-deficient (hetero)aryl halides 11 and Ai-tosylp-anisyl propargyl amine 20a, and subsequent addition of diethyl ketene acetal (106)... 

Johnson, Barnes, and McElvain (11) had treated diethyl ketene acetal with peroxide and had reported mat there was no reaction, no such... 

Since the 4-phenyl-2-methylene-l,3-dioxolane (XXl) underwent much more extensive ring opening than did the unsubstituted 2-methylene-l,3-dioxolane (I), it was reeisoned that a benzyl ketene acetal would be a more effective chain transfer agent than diethyl ketene acetal. Thus vhen methyl benzyl ketene acetal was used with styrene, a complete addition-elimination occurred to produce an oligomer of styrene. 

Molecular oxygen can add to the double bonds of olefins such as styrene, 1,1-diphenylethylene, dimethyl- and diethyl-ketene, vinyl acetate, cyclopentadiene and cyclohexadiene with formation of polymeric peroxy compounds. The course of the reaction corresponds to that of a mixed polymerization 1 r>2 3 4b d... 

The LUMOdiene HOMOalkene interaction for butadiene and methyl vinyl ether is lower than the comparable HOMOdiene-LUMOaikene interaction in dienes bearing an electron-withdrawing group. In many cases, but not all, this leads to the inverse electron demand reaction mentioned above. Fleming uses the example of azonia salt 86, which reacted with diethyl ketene acetal to give 87. Similar reaction with allyl alcohol gave 88, and acrylonitrile gave 89.97a in all cases, the reaction proceeded to 75% completion, and it is clear from the relative rates of reactions provided with each transformation that the electron-rich alkenes reacted faster. The concept of inverse electron demand applies to a Diels-Alder reaction that is controlled by the LUMO of the diene and the HOMO of the alkene, which usually means that an electron-rich alkene reacts faster than an electron-poor alkene, the opposite of what is normally observed (see above). 

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