ISSN:
0947-3440
Keywords:
[3.3](2,6)Pyridinophanes
;
Conformational analysis
;
Hydrogen bond
;
Dynamic NMR spectroscopy
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A variable-temperature 1H-NMR study and X-ray structural analysis show that the most stable conformational isomer of [3.3](2,6)pyridinophane 2 is the syn(boat-boat) conformer, and the relative stability order of the three stable conformers is syn(boat-boat) 〉 syn(chair-boat) 〉 syn(chair-chair). This is in sharp contrast to the relative stability order of the parent [3.3]metacyclophane 1: syn(chair-chair) 〉 syn(chair-boat) 〉 syn(boat-boat). The high stability of the syn(boat-boat) conformer 2c is primarily attributed to weak attractive interactions via intramolecular hydrogen bonds between nitrogen lone pairs (N-1, N-2) and the axial hydrogen atoms (2A-H, 11A-H) on the central carbon atoms of the bridges, as suggested by their short transannular distances (2.50 Å).
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199619961023
Permalink