title: Single-step synthesis of a new series of meso di-Mannich bases from the cyclic aminal (2S,7R,11S,16R)-1,8,10,17-tetraazapentacyclo[8.8.1.1.(8,17)0.(2,7)0(11,16)]icosane and p-substituted phenols.
abstract: BACKGROUND
  The results presented herein show that the cyclic aminal (2S,7R,11S,16R)-1,8,10,17-tetraazapentacyclo[8.8.1.1.(8,17)0.(2,7)0(11,16)]icosane (6), derived from cis-(meso)-1,2-diaminocyclohexane and formaldehyde, is a suitable substrate for the preption of a series of cis-meso Mannich bases such as 8a-l by reaction with p-substituted phenols 7a-l in basic media. These compounds are valuable synthetic products and may find application in asymmetric catalysis.
  
  
  RESULTS
  The products were characterized principally by NMR and IR spectroscopy. Both the benzylic and aminalic protons of the perhydrobenzimidazolidine moiety were diastereotopic due to the presence of stereogenic nitrogen centers. The occurrence of intramolecular hydrogen bonding interactions was confirmed by the broad OH stretching vibration band in the IR spectra. Vibrational spectra were calculated using B3LYP at 6-31G(d,p) level, and the calculated frequencies for the νOH vibrations were compared to those of the experimental spectra. Hydrogen bonding interactions in the solid state were observed through the X-ray crystallography of 8j. Additionally, Mulliken charges and Fukui indices for 6 were calculated as theoretical descriptors of electrophilicity.
  
  
  CONCLUSIONS
  A new series of meso Mannich bases called 4,4'-disubstituted-2,2'-{[(3aR,7aS)-2,3,3a,4,5,6,7,7a-octahydro-1H-1,3-benzimidazole-1,3-diyl]bis(methylene)} diphenols (8a-l) which are derived from cis-(meso)-1,2-diaminocyclohexane, were obtained from cyclic aminal 6. These results confirmed the behavior of 6 as an electrophilic preformed reagent in Mannich reactions in basic media.
authors.affiliation: Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Ciudad Universitaria, Carrera 30 N° 45-03, Bogotá, D.C., Colombia.
authors.forename: Augusto
authors.initials: A
authors.lastname: Rivera
authors.affiliation: Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Ciudad Universitaria, Carrera 30 N° 45-03, Bogotá, D.C., Colombia.
authors.forename: Diego
authors.initials: D
authors.lastname: Quiroga
authors.affiliation: Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Ciudad Universitaria, Carrera 30 N° 45-03, Bogotá, D.C., Colombia.
authors.forename: Jaime
authors.initials: J
authors.lastname: Ríos-Motta
authors.affiliation: Department of Solid State Chemistry, Institute of Chemical Technology, Technická 5, Prague 166 28, Czech Republic ; Institute of Physics AS CR, v.v.i., Na Slovance 2, Prague 8 182 21, Czech Republic.
authors.forename: Václav
authors.initials: V
authors.lastname: Eigner
authors.affiliation: Institute of Physics AS CR, v.v.i., Na Slovance 2, Prague 8 182 21, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Dušek