STEREOSELECTIVE s + ?2s>-DIPOLAR CYCLOADDITION OF PYRIDINIUM YLIDES TO NITRILES OF THE trans-1,3-BUTADIENE SERIES. CRYSTAL AND MOLECULAR STRUCTURE OF 3-BENZOYL-1-(2,2-DICYANO-1-CYCLOPROPYLVINYL)-2-PHENYL-6-CYANO-1,2-trans-2,3-trans-1,9-trans-1,2,3,9-TETRAHYDROINDOLIZINE

Article abstract of DOI:10.1007/BF00486803

The interaction of substituted trans-1,1-dicyano-4-phenyl-1,3-butadienes with pyridinium ylides proceeds through the path of s + ?2_s>-dipolar cycloaddition, highly regioselective and stereoselective, with formation of substituted 1-(2,2-dicyanovinyl)-2-phenyl-6-cyano-1,2-trans-2,3-trans-1,9-trans-1,2,3,9-tetrahydroindolizines.The stereoselectivity of these reactions is due to endo-addition of molecules of trans-1,3-butadienes to the anti form of pyridinium ylides; it is confirmed by correlation analysis of the data from double PMR, mathematical calculations of torsion angles, and X-ray structural studies of the substituted tetrahydroindolizines.