G. W. Gokel

Lariat ethers. 3. Macrocylic polyethers bearing donor groups on flexible arms attached at a nitrogen pivot point

Abstract The binding of lariat ethers utilizing a nitrogen pivot atom for the donor sidearm is enhanced considerably relative to the carbon-based systems and this may be explicable in terms of diminished “sidedness”

Lariat ethers. 2. The remarkable solvent dependence of binding constants in macrocyclic polyethers bearing secondary donor groups on flexible arms

Abstract Certain hydroxylated macrocyclic polyethers are found to have considerably diminished binding constants in polar solvents, even when the sidearm does not appear to be large enough to hinder the crown hole.

Lariat ethers. VI. Evidence for intramolecular chelation in sodium and potassium cation binding by 15-crown-5, carbon-pivot lariat ethers

Abstract The first compelling evidence for intramolecular sidearm involvement in sodium and potassium cation complexation by carbon-pivot lariat ethers is presented.

The effect of sidearm heteroatoms and a quaternary methyl group at the pivot position in lariat ethers

Abstract A methyl group geminal to the “pivot” carbon in hydroxy-methyl-derived lariat ethers dramatically enhances the binding afforded a complexed cation by the sidearm.

Syntheses and cation binding properties of 12-membered ring nitrogen-pivot lariat ethers

Abstract The efficient synthesis of several 12-membered ring, N-pivot lariat ethers are reported and it is shown that binding to sodium cations is generally weak except when an oligoethyleneoxy sidearm is long enough to provide additional solvation.

Conversion of arenediazonium tetrafluoroborates into unsymmetrical biaryls using catalysts other than polyethers

Abstract In addition to crown ethers and glymes which catalyze the phase transfer Gomberg-Bachmann reaction, quaternary salts, carboxylate anions, and acetonitrile cosolvent are all shown to be effective in this system.

Synthesis and properties of the first intramolecular arenediazonium cation-crown ether complex

Abstract The first intramolecular arenediazonium cation-crown ether complex is reported along with attempts to form a molecular knot from it.

Syntheses and properties of arenediazonium and anilinium cation lariat ether complexes: an “ostrich molecule” complex and evidence for intramolecular sidearm - macroring interaction

Abstract The preparation of several novel lariat ethers (macrocyclic crown polyethers having sidearms bearing pendant donor groups) is reported, These compounds are ethers derived from known 2-hydroxymethyl-15-crown-5 or -21-crown-7. The sidearms Include 2-aminophenyl, 2,4-diaminophenyl, 2-nitrophenyl, 2-(3-nitrobiphenyl), and 2-(3-aminobiphenyl). In several cases, the amino groups were converted into ammonium salts which showed substantial stabilization by intramolecular hydrogen bonding. Likewise, an -NH 2 +. ,BF 3 - complex showed evidence of intramolecular hydrogen bonding. Diazotization of the aminobiphenyl residue produced an arenediazonium cation which underwent intramolecular crown complexation, as judged by infrared spectroscopic studies to form what we call an “ostrich molecule” complex. Addition of N,N-dimethylaniline to the intramolecular arenediazonium cation complex afforded an azo compound, but europium shift reagent studies showed clearly that the diazonium cation reacted outside the macroring.

13C-NMR relaxation studies of alkali metal cryptate complexes

Abstract The 13 C spin-lattice relaxation times (T 1 s) of cryptands [2.1.1], [2.2.1] and [2.2.2] as well as those of the corresponding cryptate complexes with Li + , Na + , and K + in CDCl 3 and CH 3 OH:D 2 O (90:10) were measured and the results are interpreted in terms of molecular compression and desolvation effects.

Syntheses of Azacrowns

Almost as soon as Pedersen announced his discovery of the crown ethers (see Chaps. 2 and 3) it was recognized by many that these species were similar to those prepared by Busch and coworkers for binding coinage and transition metals (see Sect. 2.1). The latter compounds contained all or a predominance of nitrogen and sulfur (see also Chap. 6) in accordance with their intended use. The crown ethers and the polyazamacrocycles represented two extremes in cation binding ability and preparation of the intermediate compounds quickly ensued. In the conceptual sense, monoazacrowns are the simplest variants of the macrocyclic polyethers and these will be discussed first.