14098-41-0Relevant academic research and scientific papers
Application of Bayer-Villiger reaction to the synthesis of dibenzo-18-crown-6, dibenzo-21-crown-7 and dihydroxydibenzo-18-crown-6
Utekar, Druman R.,Samant, Shriniwas D.
, p. 193 - 197 (2014/05/06)
Dibenzo-18-crown-6, dibenzo-21-crown-7 and dihydroxy dibenzo-18-crown-6 were synthesized by Bayer-Villiger oxidation strategy. Dibenzo-18-crown-6 and dibenzo-21-crown-7 could be synthesized through a three-step protocol starting from salicylaldehyde. Salicylaldehyde was reacted with bis-(2-chloroethyl)ether using K2CO3 in acetonitrile to link the two phenolic groups with the oxyethylene bridge followed by conversion of the formyl group to the hydroxy group via a Baeyer-Villiger reaction and finally linking the two phenolic group with appropriate oxyethylene bridge. The two target crown ethers were obtained in overall yield, 24% and 30%, respectively. This method has a great potential for synthesis of symmetrical as well as unsymmetrical dibenzo crowns with varying oxyethylene bridges. Baeyer-Villiger oxidation could be used to prepare dihydroxy derivative of dibenzo-18-crown-6 through acetylation of dibenzo-18-crown-6 followed by Baeyer-Villiger oxidation. The Baeyer-Villiger oxidation could be substantially accelerated using trifluoroacetic acid.
Preparation of benzo- and polybenzocrown ethers by macrocyclization reactions
Hanes, Robert E.,Lee, Jong Chan,Ivy, Sheryl N.,Palka, Anna,Bartsch, Richard A.
, p. 238 - 248 (2012/11/07)
Macrocyclization of crown ethers and their methods of preparation were explored. We present a robust, scalable method for the preparation of these macrocycles. Additionally, the effect of changing the structures of the precursors was explored to determine whether the 'cut' of bisphenol and dimesylate influenced the course of the reaction as measured by the yield. Further, using catechol derivatives, the method was used for the preparation of monobenzocrown ethers. Interestingly, for the preparation of monobenzocrown ethers, [2+2] adducts were discovered to be significantly contaminating the products. Dimesylates were chosen as the leaving group due to their ease or preparation and the ability to use the unpurified products with no apparent impact on the macrocyclization.
An Improved Method for Preparing Dibenzo Crown Ethers
Kotlyar,Gorodnyuk,Grigorash,Chuprin
, p. 1135 - 1138 (2007/10/03)
In synthesis of symmetrical and unsymmetrical dibenzo crown ethers, the use of dimethyl sulfoxide as a solvent in cyclization allows an increase in the yields, a significant reduction in the reaction time, and simplification of refining.
The Complexation of the Diquat Dication by Dibenzo-3n-crown-n Ethers
Colquhoun, Howard M.,Goodings, Eric P.,Maud, John M.,Stoddart, J. Fraser,Wolstenholme, John B.,Williams, David J.
, p. 607 - 624 (2007/10/02)
Spectrophotometric investigations of equimolar mixtures of diquat bis(hexafluorophosphate) (2) and a range of dibenzo-3n-crown-n ethers in acetonitrile reveal the existence of charge-transfer absorption bands at ca. λmax 400 nm.These absorptions are attributable to intermolecular ?-? charge transfer between the electron-rich catechol units of the dibenzo-crown ethers and the electron-deficient bipyridinium ring system of the diquat dication.The qualitative conclusion from these experiments, that the most stable 1:1 complex is formed between dibenzo-30-crown-10 (14) and diquat bis(hexafluorophosphate) (2), led to the isolation from dichloromethane methanol-n-heptane of red crystals of 2 suitable for X-ray crystallography.Although the crystal structure analysis revealed that there are two independent sets of 1:1 complexes (I and II) in the unit cell, the gross structural features of the two complexes are very similar.In addition to the paralell alignment of their three aromatic rings to accommodate the stabilising intermolecular ?-? charge-transfer interaction, there is probably some further host-guest stabilisation to be gained on account of favourable electrostatic interactions between the phenolic oxygen atoms in the host and the nitrogen atoms in the pyridinium rings of the guest.Moreover, there is some evidence for weak C-H...O hydrogen bonding involving principally H-6 and H-6' on the bipyridinium ring system of the guest and certain -CH2OCH2- oxygen atoms in the host.As evidenced by 1H n.m.r. spectroscopy in CD3COCD3, these non-covalent bonding interactions are probably responsible for the formation of stable and ordered 1:1 complexes with similar gross structural features in solution, at least in the cases where dibenzo-30-crown-10 (14), dibenzo-33-crown-11 (15), and dibenzo-36-crown-12 (16) are the hosts.Further evidence for the 1:1 stoicheiometry of these solution complexes, as well as for the complex involving dibenzo-27-crown-9 (13), has come from equilibrium constant measurements for the association between the dibenzo-3n-crown-n (n = 9-12) hosts (13)-(16) and diquat bis(hexafluorophosphate) (2) in acetone.A quantitative treatment of the charge-transfer absorption bands at 400 nm, which affords Ka values of 410, 17500, 10800, and 2000 M-1 for n = 9, 10, 11, and 12, respectively, provides convincing quantitative evidence for (a) 1:1 stoicheiometry and (b) the relative stabilities of the 1:1 complexes in solution.In the case of dibenzo-24-crown-8 (11), a complex of 2:1 (guest-host) stoicheiometry is believed to be formed in acetone with a Ka value of 385000 M-2, as shown by a successfull quantitative treatment of the charge-transfer absorption data by an independent method.
