1127-08-8Relevant academic research and scientific papers
Hydrazide-Based Quadruply Hydrogen-Bonded Heterodimers. Structure, Assembling Selectivity, and Supramolecular Substitution
Zhao, Xin,Wang, Xiao-Zhong,Jiang, Xi-Kui,Chen, Ying-Qi,Li, Zhan-Ting,Chen, Guang-Ju
, p. 15128 - 15139 (2007/10/03)
This paper describes the synthesis, self-assembly, and characterization of a new class of highly stable hydrazide-based quadruply hydrogen-bonded heterodimers. All of the hydrazide-derived heterodimers possess the complementary ADDA-DAAD hydrogen-bonding sequences. Hydrazide derivatives 1, which has two intramolecular S(6) RO...H-N hydrogen bonds, and 2 complex to afford two fastly exchanging isomeric heterodimers 1·2 and 1·2′ in chloroform, as a result of two different conformational arrangements of 2. An average binding constant Kassoc of 4.7 × 104 M-1 was determined for heterodimer 1·2 and 1·2′ by 1H NMR titration of 1 with changing 2 in chloroform-d. In contrast, 1 binds 11 and 12, both of which are introduced with two intramolecular S(6) hydrogen bonds, to exclusively afford heterodimers 1·11 and 1·12, with Kassoc values of 1.8 × 104 and 5.0 × 102 M-1, respectively. Fluorine-containing 19, which has a hydrazide skeleton identical to that of 1 but two intramolecular S(6) F...H-N hydrogen bonds, can also complex with 2, 11, and 12, to afford heterodimers 19·2, 19·2′, 19·11, and 19·12, with Kassoc values of of 1.2 × 104 (average value for 19·2 and 19·2′), 5.4 × 103, and 1.9 × 102 M-1, respectively. The structures of the new heterodimers have been proven with NOESY, IR, and VPO (for some of the heterodimers) experiments. Moreover, 1 and 19 can also strongly bind 2,7-dilauroylamido-1,8-naphthyridine 23 to afford dimers 1·23 and 19·23 with Kassoc values of 6.0 × 105 and 1.4 × 105 M-1, respectively. Adding 1 to the 1:1 solution of 23 and 1-octyl-3-(4-oxo-3,4-dihydro-pyrido[2,3-d]pyrimidin-2-yl)urea 24 or 1-octyl-3-(4-oxo-1,4-dihydropyrimidin-2-yl)urea 25, which had been developed initially by Zimmerman and Meijer, respectively, induces dimers 23·24 and 23·25 to dissociate, leading to the formation of dimers 1·23 and 24·24 or 25·25, respectively. The new hydrazide-based hydrogen-bonding modules described are useful building blocks for self-assembly and open a new avenue to recognition between discrete supramolecular species.
Selective reactions of 1,1-cycloalkanedicarboxylic acids with SF4. a route to 1,1-bis(trifluoromethyl)cycloalkanes, 1-fluoroformyl-1-(trifluoromethyl)cycloalkanes and 1-(trifluoromethyl)-1-cycloalkanecarboxylic acids
Dmowski, Wojciech,Wolniewicz, Adam
, p. 141 - 146 (2007/10/03)
Six-, five-, four- and three-membered 1,1-cycloalkanedicarboxylic acid (2a-d) were synthesized by alkaline hydrolysis of the corresponding diesters (1a-d) and the reactions of the formers with SF4 were investigated. 1,1-Bis(trifluoromethyl)cycloalkanes (3a-d) were the products of the reactions conducted at 120-150°C while at 30°C 1-fluoroformyl-1-(trifluoromethyl)cycloalkanes (4a-d) were exclusively formed. The latter were isolated as pure compounds or converted in situ into 1-(trifluoromethyl)-1-cycloalkanecarboxylic acids (5a-d).
