Veronica K. Majestic

Synthesis, conformational novelty, and x-ray crystal structure of the spherical .

Abstract The synthesis and x-ray crystal structure of a spherical cryptand 2 , in which the bridgehead N -electrons are in the in - in configuration and one of the pyridine rings is located inside the cavity of the cryptand, are described.

Pyridinophanes, pyridinocrowns, and pyridinocryptands

In general, the pyridinophanes, pyridinocrowns, and pyridinocryptands have been surveyed. The pyridinophanes have been limited to those containing carbon bridging units of two atoms or less. In these instances the pyridinophanes may be bridged at the 2,6-, 3,5-, or 2,5-positions. The pyridinocrowns discussed contain carbon and nitrogen heteroatoms or nitrogen and oxygen heteroatoms and are bridged at only the 2,6-positions. The pyridinocrowns containing only oxygen or sulfur have not been included in this discussion. The discussion of the pyridinocryptands has not been restricted, since there are currently only a limited number of cryptands of this type.

The crystal structure of a macrocycle containing pyridine and piperazine subunits, and of a Cu(I) complex of its diprotonated cation

The 2:2 macrocycle C22H30N6, containing pyridine and piperazine subunits, crystallizes in monoclinic space group C2c with a = 17.614(3), b = 9.696(2), c = 12.662(2) A, β = 111.65(2)°, V = 2010(1) A3, Z = 4. The structure was refined to R = 0.036 for 1863 observed reflections. The molecule lies on an inversion center, and the piperazine subunits have the chair conformation. Surprisingly, this macrocycle becomes diprotonated, and the Cu(II) is reduced to Cu(I) upon reaction with CuCl2 in methanol. The resulting Cu(I) complex of the diprotonated macrocyclic dication, [CUCl(C22H32N6)]Cl2·2H2O, crystallizes in monoclinic space group P21n with a = 10.745(1), b = 13.728(2), c = 17.774(2) A , β = 98.08(1)°, V = 2596(1) A3, Z = 4. The structure was refined to R = 0.058 for 3989 observed reflections. The Cu atom coordinates approximately linearly to one of the pyridine N atoms and a chloro ligand with CuN distance 1.947(3) A, CuCl distance 2.133(1) A, and NCuCl angle 164.5(1)°. While the piperazine subunits maintain their chair conformations, one N of each is protonated and turned outward. The unprotonated piperazine N atoms form long interactions of 2.488(4) and 2.508(4) A, distance to the Cu atom.

A convenient synthesis of spherical cryptands by a quaternization-dealkylation procedure.

Abstract The construction of spherical cryptands has been accomplished from bis -diamines by a stepwise quaternization-demethylation sequence. Cryptands with diverse bridges can be easily prepared by this procedure.

Isosucrose. Definitive structural assignment by spectral correlation to α,β- and α,α-sucrose octaacetates

Abstract Three nonreducing disaccharides containing D -glucosyl and D -fructosyl groups, namely, “isosucrose” octaacetate ( 3 ), sucrose octaacetate ( 4 ), and “α,α-sucrose” octaacetate ( 5 ), give qualitatively identical mass spectra and are, therefore, related as diastereoisomers. Spin-coupling values in the 300-MHz n.m.r. spectra of 3 , 4 , and 5 establish that the D -glucopyranosyl group is present in the 4 C 1 ( D ) conformation, and that the anomeric configuration of this group is α in 4 and 5 , and β in 3 . In the n.m.r. spectra, the H-4 atom of the D -fructofuranosyl group of 3 and 5 resonates 0.5 p.p.m. upfield of the corresponding signal of 4 , from which it was deduced that both 3 and 5 are α- D -fructofuranosides.

The crystal structures of a macrocycle containing 2,6-pyridino and piperazino subunits and of the tetrachlorocobaltate(II) salt of its diprotonated cation

The multiheteromacrocycle C26H38N6O4 is prepared by reaction of 2,6-dichloropyridine with NN′-bis-(2-hydroxyethyl)piperazine. Counter data obtained from crystals of space group P21/c having a= 10.498(3), b= 4.748(2), c= 26.032(8)A, β= 96.42(2)°, and Z= 2 were used in the refinement, which converged with R 0.043 for 1 060 observed data. The molecule possesses crystallographic Ci symmetry with the piperazino subunits in the chair conformation. Reaction of this macrocycle with CoCl2 has led to diprotonation. Crystals of [C26H40N6O4][CoCl4] conform to space group P21/c with a= 15.258(6), b= 28.676(12), c= 15.538(5)A, β= 107.18(3)°, and Z= 8. Refinement using 2 239 observed data measured on a diffractometer has yielded R 0.108. The crystal structure consists of [C26H40N6O4]2+ ions having essentially identical conformations to the macrocycle C26H38N6O4, each forming two hydrogen bonds to tetrahedral [CoCl4]2– ions. The Co–Cl distances within the complex anions average 2.260(8)A. The array of [CoCl4]2– anions approximates a C-centred structure with the true b axis halved.