Improved receptors for dibutylmalonic acid

Acid−Amide Intermolecular Hydrogen Bonding

“…The O···O and N···O distances in 1 (2.55 and 2.79 Å) may also be compared to the intramolecular mean values of 2.61 and 2.64 Å (O···O) and 2.84 and 2.87 Å (N···O) in bilirubin 14b and mesobilirubin,14c respectively. Similar (amide) H···O (carboxyl) distances, 1.88−2.14 Å, are found in the complexes of bis(amidopyridines) with dicarboxylic acids of varying chain length;18e in these complexes, the second H-bond in the 8-membered ring is (carboxyl) H···N (pyridine), 1.60−2.33 Å. The lactam−carboxyl cyclic grouping found in 1 implies stronger intermolecular hydrogen bonds than those in lactam dimers, in which typical N···O distances are about 2.82 Å …”

“…In the crystal, 1 forms dimers, joined in (8) patterns (8-membered rings with 2 donors and 2 acceptors) by N−H···O and O−H···O hydrogen bonds, across a center of symmetry (see Figure ). Coordinates for the compounds in refs g and c for use in Table were obtained from the Cambridge Structural Database …”

“…More recently, amide to carboxylic acid hydrogen bonds have become important in molecular recognition chemistry, where amide hosts have been designed and constructed for binding carboxylic acid and carboxylate ion guests. However, in only two examples 18b,c is the amide carbonyl designed to be a part of the hydrogen bonding motif (as in Figure C).…”

“…In one of the two relevant examples 18c the acid carbonyl is hydrogen bonded to two amide N−H groupsan arrangement similar to that observed in dipyrrinones (Figure , parts D and E). There are extremely few examples of carboxylic acid to amide hydrogen bonding of the type shown in Figure C; among them are several cyclic amide−carboxylic acid complexes. 13b,18f-h,20c One such arrangement is the linkage between two molecules of 6-methyluracil-5-acetic acid 18h. Another is the involuntary intramolecular carboxylic acid to amide (Figure C) hydrogen bonding studied by Rebek and coworkers 13b in a cleverly-designed system involving a monoamide derivative of m -xylidenediamine bis(Kemp's triacid) imide.…”

Substituted 9-Diethylaminobenzo[a]phenoxazin-5-ones (Nile Red Analogues): Synthesis and Photophysical Properties

“…Yet, the tetralone approach necessitated scalding temperatures and starting materials that were not easily accessible. The 7-nitro and 7-bromo-1-tetralones (for the syntheses of 6d and 6e ) were successfully obtained by nitration and bromination of α-tetralone, , respectively. In the case of 7-cyano-1-naphthol ( 6f ), this novel compound was successfully synthesized from 7-bromo-1-naphthol ( 6e ) upon the action of CuCN under Rosenmund–von Braun conditions …”