Dipivaloylketene and Its Dimers. [2+4] versus [2+2] Cycloaddition Reactions of α-Oxo Ketenes

Kappe C.O., Farber G., Wentrup C. and Kollenz G. (1992) Dipivaloylketene and Its Dimers. [2+4] versus [2+2] Cycloaddition Reactions of α-Oxo Ketenes. Journal of Organic Chemistry, 57 26: 7078-7083. doi:10.1021/jo00052a018


Author Kappe C.O.
Farber G.
Wentrup C.
Kollenz G.
Title Dipivaloylketene and Its Dimers. [2+4] versus [2+2] Cycloaddition Reactions of α-Oxo Ketenes
Journal name Journal of Organic Chemistry   Check publisher's open access policy
ISSN 1520-6904
Publication date 1992-12-01
Year available 1992
Sub-type Article (original research)
DOI 10.1021/jo00052a018
Open Access Status Not yet assessed
Volume 57
Issue 26
Start page 7078
End page 7083
Total pages 6
Place of publication WASHINGTON
Publisher AMER CHEMICAL SOC
Language eng
Abstract Dipivaloylketene (8) is generated by preparative flash vacuum pyrolysis of furandione 6. While dimerization of 8 in apolar and several polar solvents leads to the previously reported [2 + 4] dimer 7, dimerization in the presence of DMSO, tributylphosphine oxide, or pyridine instead surprisingly occurs across the C=O bond of the ketene function, affording dioxinone 9. This is a novel type of alpha-oxo ketene dimerization. The reversibility of both dimerizations and mechanistic pathways for the formation of 9 are discussed. Cycloaddition reactions of 8 with heterocumulenes 10a,b and 12a-c yield [2 + 4] cycloadducts 11a,b and 13a-c, respectively. Oxazinones 13a-c can add a second molecule of 8 to generate novel spiro heterocycles 14a-c. In contrast, oxo ketene 7 reacts with carbodiimides 12a,b, to furnish [2 + 2] adducts 15a,b. This is the first unequivocal example of a direct [2 + 2] cycloaddition reaction of an alpha-oxo ketene. The unexpected formation of these compounds was confirmed by X-ray crystallography (15a). General aspects of [2 + 2] versus [2 + 4] cycloaddition in alpha-oxo ketenes are discussed.
Keyword Cyclic Oxalyl Compounds
Heterocyclic-Compounds
Methyl Ketones
Ketenes
Derivatives
1,3-Dioxin-4-Ones
Esters
Decarbonylation
Chemistry
"2,2,6-Trimethyl-4H-1,3-Dioxin-4-One
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: Scopus Import - Archived
 
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