[2+2] Versus [4+2] Cycloaddition Reactions of 1,3-Diaza-1,3-butadienes with Various Mono- and Disubstituted Ketenes and Supporting Mechanistic Considerations
The cycloaddition behavior of dihydropyrazines towardketenes was investigated using single-crystal X-ray structures of the cycloadducts and density functional theory (DFT) calculation data. The reaction proceeds via a stepwise pathway involving an orientation complex prior to formation of the betaine intermediate. This is followed by electrocyclization to afford the 1 : 1 and 1 : 2 adducts bearing
Stepwise Reactions between Cyclic 1,4-Diazadienes and Ketenes: Characteristics and Mechanism
作者:Kazuhide Nakahara、Koki Yamaguchi、Hisao Kansui
DOI:10.3987/com-20-14401
日期:——
The reaction of unsymmetrical monophenyl cyclic 1,4-diazadienes with ketene derivatives yields new structures via 1,5-sigmatropic reactions. These structures were determined and confirmed by single-crystal X-ray analysis. The reactionmechanism was investigated by density functional theory calculations. The result of the calculation indicated whether the reaction was a cyclization reaction or a 1,5-shift
Pericyclic Reaction of Ketenes with Cascade Reaction Products of Pyridine N-Oxides and Dipolarophiles. X-Ray Structures of the Adducts and Formation Mechanism
The structures of the adducts derived from the reactions of substituted ketenes with dihydropyridine derivatives have been clarified by single crystal X-ray analyses and the formation mechanism is discussed on the basis of the reaction-path calculations by semiempirical and density functional theory (DFT) molecular orbital methods.