Synthesis, X-ray crystallography, and computational analysis of 1-azafenestranes.
The tandem [4+2]/[3+2] cycloaddition of nitroalkenes has been employed in the synthesis of 1-azafenestranes, molecules of theoretical interest because of planarizing distortion of their central carbon atoms. The synthesis of c,c,c,c-[5.5.5.5]-1-azafenestrane was completed in good yield from a substituted nitrocyclopentene, and its borane adduct was analyzed through X-ray crystallography, which showed a moderate distortion from ideal tetrahedral geometry. The syntheses of two members of the [4.5.5.5] family of 1-azafenestranes are also reported, including one with a trans fusion at a bicyclic ring junction which brings about considerable planarization of one of the central angles (16.8 degrees deviation from tetrahedral geometry). While investigating the [4.5.5.5]-1-azafenestranes, a novel dyotropic rearrangement that converts nitroso acetals into tetracyclic aminals was discovered. Through conformational analysis, a means to prevent this molecular reorganization was formulated and realized experimentally with the use of a bulky vinyl ether in the key [4+2] cycloaddition reaction. Finally, DFT calculations on relative strain energy for the 1-azafenestranes, as well as their predicted central angles, are disclosed.
Denmark
Scott E
SE
Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA. denmark@scs.uiuc.edu
Montgomery
Justin I
JI
Kramps
Laurenz A
LA
D001372:Aza Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D003500:Cyclization; D003521:Cyclopropanes / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011083:Polycyclic Compounds / Q000737:chemistry*; D013237:Stereoisomerism
D001372:Aza Compounds; D001643:Bridged Bicyclo Compounds; D003521:Cyclopropanes; D011083:Polycyclic Compounds