Two bifunctional concave acid-base catalysts, 1 and 2, have been synthesized starting from 2,6-dibromopyridine (9) and 2,6-bis(omega-alkenyloxy)phenylboronic acids 8 and 10 which end up as bridgeheads in final bimacrocycles 1 and 2. One bridgehead contained an additional substituent in the 4-position. The respective protected 4-hydroxymethyl-substituted phenylboronic acids 8 were synthesized from 4-bromo-3,5-dihydroxybenzoic acid (3) in five steps. 4-Unsubstituted boronic acid 10 and 4-substituted boronic acid 8 were then attached to 9 by subsequent Suzuki couplings to give tetra-omega-alkenes 12. By ring-closing metathesis of 12, bimacrocyclic dienes 13 and 17 were formed. After deprotection of the 4-hydroxymethyl group of one bridgehead, a 3-hydroxybenzoate was coupled to 14 to give ester 15 which gave bifunctional acid-base catalyst 1 upon hydrolysis. Analogously, homologue 2 was synthesized, but before coupling the bi-macrocycle to the benzoate,. tetraene 14 was hydrogenated to 18. Acidic and basic centers in 1 (49% from 9) and 2 (19% from 9) are at least 5 angstrom apart. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).
New 2'-substituted2,2",6,6"-tetramethyl-1,1':3',1"'-terphenyls have been synthesized. Solubility of concave acids 4b-6b could be enhanced by substitution in 4 and 4" position, allowing the study of hydrogen-bonded heterodimers. Concave acids show larger binding constants for 2-amidopyridines 7 than non-macrocyclic ones, probably due to the prevention of homodimer formation by the macrocyclic shielding. New 2,6-diarylbenzyl alcohols 1d, 8d and 9d have been synthesized and tested in protonation reactions. New functional groups were introduced into the 2' position: OH (phenols 1f and 12f) and NH2 ( aniline 1j). The basicity of aniline 1j in ethanol was determined by titration and was compared to other bases. Also sulfonic acids 1l and 17l were prepared, and the corresponding methyl esters 1m and 17m were tested as methylating agents.
AbstractFor Abstract see ChemInform Abstract in Full Text.
AbstractFor Abstract see ChemInform Abstract in Full Text.
Twelve new mono- or diaryl-substituted 1,10-phenanthrolines (17 and 18) have been synthesized. The key step is a Suzuki coupling reaction between the substituted areneboronic acids 6, 11, and 15 and the mono- and dihalo-1,10-phenanthrolines 16. The syntheses of bis-ortho-substituted boronic acids 6, 11, and 15 from substituted arenes 5 or substituted bromoarenes 10 and 14 by lithiation and subsequent treatment with trimethyl borate is described.. Not only 2,9-diiodo- (16c) but also 2,9-dichloro-1,10-phenanthroline (16b) can be used with good yields (65-92%) in the described Suzuki coupling. For the syntheses of unsymmetrically substituted 1,10-phenanthrolines 18b, 18i, and 18j, the use of 2-chloro-9-iodo-1,10-phenanthroline is not necessary; two different bis-ortho-substituted arene rings can be introduced stepwise in 46 to 64% total yield. ((C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
