Cycloaddition of (N-alkyl-N-phenylamino)ketene with imines
摘要:
(N-Alkyl-N-phenylamino)ketenes were prepared in the presence of various imines, and a [2 + 2] cycloaddition reaction occurred to yield 3-(N-alkyl-N-phenylamino)-2-azetidinones. The size and electronic nature of the imine substituents were varied in order to probe those factors that influence the stereochemistry of the cycloaddition. The stereochemistry of the 2-azetidinone was determined by the substitution pattern of the imines. In general, the stereochemistry of the 2-azetidinone products are significantly influenced by the bulk of the N substituent on the imine. These results are discussed in terms of a two-step zwitterionic intermediate.
Cycloaddition of (N-alkyl-N-phenylamino)ketene with imines
摘要:
(N-Alkyl-N-phenylamino)ketenes were prepared in the presence of various imines, and a [2 + 2] cycloaddition reaction occurred to yield 3-(N-alkyl-N-phenylamino)-2-azetidinones. The size and electronic nature of the imine substituents were varied in order to probe those factors that influence the stereochemistry of the cycloaddition. The stereochemistry of the 2-azetidinone was determined by the substitution pattern of the imines. In general, the stereochemistry of the 2-azetidinone products are significantly influenced by the bulk of the N substituent on the imine. These results are discussed in terms of a two-step zwitterionic intermediate.
Under the catalysis of Yb(OTf)3, the cyclization of iminium-ion intermediates and imines was promoted through the aza-Diels-Alder mechanism, providing a simple reaction for the synthesis of tetrahydroquinoline-iminosugars derivatives with good stereoselectivity. The absolute structures of compounds 1 a and 5 a were confirmed by single crystal X-ray diffraction and 2D NMR.
Cycloaddition of (N-alkyl-N-phenylamino)ketene with imines
作者:William T. Brady、Mohammad M. Dad
DOI:10.1021/jo00021a029
日期:1991.10
(N-Alkyl-N-phenylamino)ketenes were prepared in the presence of various imines, and a [2 + 2] cycloaddition reaction occurred to yield 3-(N-alkyl-N-phenylamino)-2-azetidinones. The size and electronic nature of the imine substituents were varied in order to probe those factors that influence the stereochemistry of the cycloaddition. The stereochemistry of the 2-azetidinone was determined by the substitution pattern of the imines. In general, the stereochemistry of the 2-azetidinone products are significantly influenced by the bulk of the N substituent on the imine. These results are discussed in terms of a two-step zwitterionic intermediate.