Showing papers by "J. Fraser Stoddart published in 1976"

Chiral crowns incorporating pyridyl units and tertiary amine functions

Abstract: The chiral hosts DD-(1) and DD-(7) have been synthesised and the temperature dependence of the 1H n.m.r. spectrum of the 1:1 complex between DD-(1) and benzylammonium thiocyanate in solution has been interpreted in terms of slow dissociation of the complex.

Enantiomeric differentiation by chiral macrocyclic polyethers derived from D-mannitol and binaphthol

Abstract: The chiral macrocyclic polyethers (R)-D-(5) and (S)-D-(5) derived from D-mannitol and (R)- and (S)- binaphthol respectively exhibit comparable enantiomeric selectivities in complexing (±)-(RS)-α-phenylethylammonium hexafluorophosphate under equilibrium conditions.

Conformational behaviour of medium-sized rings. Part III. Heterocyclic analogues of 12,13-dihydro-11H-dibenzo[a,e]cyclononene, 6,11,12,13-tetrahydro-5H-dibenzo[a,e]cyclononene, and 5,6,7,12,13,14-hexahydrodibenzo[a,f]cyclodecene

Abstract: The temperature dependence of the 1H n.m.r. spectra of a number of heterocyclic analogues (3a–c) of 12,13-dihydro-11H-dibenzo[a,e]cyclononene has been interpreted in terms of the interconversion of chair- and boat-like conformations. Conformational analysis on these molecules has been carried out with the aid of strain energy calculations on the thia-analogue (3c); in this case a useful correlation between calculated and experimental activation parameters was found. Variable temperature 1H n.m.r. spectroscopy and strain energy calculations have demonstrated that the heterocyclic analogues (4a–f) and (5a–d) of 6,11,12,13-tetrahydro-5H-dibenzo[a,f]-cyclononene and 5,6,7,12,13,14-hexahydrodibenzo[a,f]cyclodecene, respectively, all adopt flexible chair-like conformations with C2 symmetry which undergo an inversion process involving torsion about single bonds.