title: Facile, regioselective [4 + 2] cycloaddition involving 1-aryl-4-phenyl-1-azadienes and allenic esters: an efficient route to novel substituted 1-aryl-4-phenyl-1,4-dihydropyridines.
abstract: [reaction: see text]1-Aryl-4-phenyl-1-azadienes undergo facile, regioselective [4 + 2] cycloaddition to the C2,C3 pi-bond of allenic esters in refluxing benzene, and the formed adducts undergo a 1,3-H shift to afford novel 2-alkyl-1-aryl-3-ethoxycarbonyl-4-phenyl-1,4-dihydropyridines (78-97%). However, when the reaction is carried at room temperature, besides the [4 + 2] addition, the [2 + 2] mode of addition involving C=N of azadiene and C3,C4 pi-bond of allenic esters also intervenes. The resulting N-aryl-2-ethoxy-carbonyl-methylidene-4-styrylazetidines (17-28%) undergo reorganization on silica gel to afford 2-cyclohexen-1-ones.
authors: Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar-143 005, Punjab, India. mpsishar@angelfire.com
authors: M P
authors: MP
authors: Ishar
authors: K
authors: K
authors: Kumar
authors: S
authors: S
authors: Kaur
authors: S
authors: S
authors: Kumar
authors: N K
authors: NK
authors: Girdhar
authors: S
authors: S
authors: Sachar
authors: A
authors: A
authors: Marwaha
authors: A
authors: A
authors: Kapoor