Dibenzo-18-crown synthesis

Casnati, A., Sansone, F., Dozol, J.F. 2001. New calyx[4]arene-monobenzo- and dibenzo-crown-6 as cesium selective ionophores in the radioactive waste treatment Synthesis, complexation and extraction properties. J. Inch Phenom. Macro. Chem, 41 (1-4) 193-200. 

Hdgberg and Cram (1975) and Biernat and Luboch (1984) prepared some dibenzodiaza-, triaza-, and tetraaza-crowns from a bis-tosylanilide derivative prepared from o-nitrophenol (method V-7). This procedure allows the synthesis of dibenzo-crowns containing from two to four nitrogen atoms de-... 

In addition to PPy and PTh derivatives, numerous reports have focused on the synthesis and the properties of electroactive polymer films electrogenerated from the oxidation of crown ether-substituted benzenes [273-286] and naphthalenes [17, 287-293]. Among them, poly(dibenzo-crown ether)s and, especially, poly(dibenzo-18-crown-6) have been the most extensively studied, owing to their remarkable structural, electrochemical, and complexing properties [278-280]. Furthermore, their affinity for a large variety of cations, including heavy metal and precious metal cations, was greatly improved when they were previously undoped [281-286]. 

Method X (Eq. 3.3) is almost a corollary to method V since the stoichiometry is identical. In fact, it is not the intention, but the size of the crown which will determine the outcome of the reaction. For example, the synthesis of dibenzo-18-crown-6 (Eq. 

From their structures, it appears that the hydrolytic stability of macrocyclic lactones must necessarily be inferior to macrocyclic polyethers. Ease of synthesis of the cyclic esters is therefore one of the aspects which commend them to interest. It is probably for this reason that such lactones have not been made more often by the interesting approach of Kdgel and Schroder . These workers report the ozonolysis of dibenzo-18-crown-6 in a mixture of methanol and dichloromethane at —20°. Reduction of the ozon-ide at —75° using dimethylsulfide followed by warming and addition of acetone led to formation of 6 in 14% yield. The bis-oxalate had mp 164—165° from acetone, very similar to that of the starting crown. The transformation is illustrated below in Eq. (5.9). 

J.-P. Bourgeois, P. Seiler, M. Fibbioli, E. Pretsch, F. Diederich, L. Echegoyen, Cyclophane-Type Fullerene-dibenzo [18] crown-6 Conjugates with trans-1, trans-2, and trans-3 Addition Patterns Regioselective Templated Synthesis, X-ray Crystal Structure, Ionophoric Properties, and Cation-Complexation-Dependent Redox Behavior , Helv. Chim Acta 1999, 82,1572-1595. 

Figure B. Pictorial representation of the self-assembly of pseudorotaxa-nes based on (a) charge-transfer and C-H—O hydrogen-bonding interactions between 1,1 -diben-zyl-4,4 -bipyridinium dication and 1,5-dinaphtho[38] crown-10 (1/5DN38C10), and (b) hydrogen-bonding interactions between dibenzyl ammonium ion and dibenzo[24]crown-8 (DB24C8). A possible route towards the synthesis of rotaxanes and catenanes is also schematized.

Scheme 3.2 Accidental synthesis of the first crown ether, dibenzo [18] crown-6.4...

A look at the original synthesis of dibenzo[18] crown-6 (Scheme 3.2) suggests a possible side reaction that might have resulted in the crown ethers never being discovered at all. The fortuitous macrocycle dibenzo [18] crown-6 that gave birth to modern supra molecular chemistry might never have formed... 

Atwood, J. L., Junk, P. C., Synthesis and X-ray crystal structures of oxonium ion complexes of 21-crown-7 and dibenzo-30-crown-10. J. Chem. Soc., Dalton Trans. 1997, 4393-4399. 

Synthesis of mesoporous TiO/M composites and their photocatalytic activity in hydrogen evolution. Hydrolysis of Ti(TV) tetrabutoxide with subsequent sol-gel transformation in the presence of dibenzo-18-crown-6 ether as a template yields amorphous titanium dioxide (Fig. 1). Calcination of the parental amorphous sample at 500 °C causes crystallization of Ti02 and formation of a porous material with high specific surface area and a narrow pore size distribution with the average pore diameter 5.0 nm (Table 1, sample No. 2). Combination of the hydrothermal treatment (HTT) of Ti02 samples at 100 - 175 °C with their subsequent calcination... 

Both activation by Cr(CO)3 complexation and the use of phase-transfer conditions are necessary for success in the following synthesis. A cyclic bis-ether can easily be obtained from the o-dichlorobenzene complex 18a (Scheme 14). Indeed, reaction of 18a with Na[0(CH2)2]20H in (MeOCH2)20 and with Bu4NBr as a phase-transfer catalyst at 50 °C for 8 h, followed by decomplexation with I2 directly affords dibenzo-18-crown-6 35 in 27 % yield. Compound 34, which can also be converted into 35, can be obtained in 84 % yield by heating 18a, NaH, and diethylene glycol for 24 h in DME at 50 °C [19]. The authors demonstrated the potential of this synthesis by preparing different crown ethers with various heteroatoms. 

Fig. 4.6. (Top) Reaction that eventually led to the serendipitous synthesis of dibenzo-18-crown-6 ether. (Middle) common crown ethers with their usual denomination. (Bottom) some cryptands with their denomination.

Bazan reported the synthesis, structure, and photophysical behavior of a number of boratastilbene derivatives, which are highly emissive in the presence of donor solvents or when crown ethers are added. Extended conjugation in the bifunctional species (156) results in an absorption maximum at 396 nm, which is red-shifted by 55 nm relative to that of the monoftmctional boratastilbene. The change in the absorption and emission spectra upon addition of dibenzo-18-crown-6 suggests a distinct effect of the counterions and of aggregation phenomena on the photophysical properties of these species. 

Figure 2.27 ORTEP diagram of [Na(DB18C6)H20][Tb(L )2] with the thermal ellipsoids drawn at the 30% probability level and the hydrogen atoms removed for clarity [59]. (Reprinted with penmssion from P.N. Remya, S. Bijn, M.L.P. Reddy, A.H. Cowley and M. Findlater, ID Molecnlar ladder of the ionic complex of terbinm-4-sebacoylbis( 1 -phenyl-3-methyl-5-pyrazolonate) and sodium dibenzo-18-crown-6 synthesis, crystal structure, and photophysical properties, Inorganic Chemistry, 47, 7396-7404, 2008. 2008 American Chemical Society.)...

The type of phase-transfer catalyst plays a key role in the phase-transfer catalytic synthesis of l-bromo-1-chlorocyclopropanes, which are formed in good yields and with high selectivity if the reaction of dibromochloromethane with an alkene is performed using a crown ether (dibenzo-18-crown-6, " 3,5-di-fer/-butylbenzo-15-crown-5, " " 3,3, 5,5 -tetra-tert-butyldiben-zo-lS-crown-b ) or tetramethylammonium chloride.For the specific effect of the tetra-methylammonium chloride on the dichlorocyclopropanation of unconjugated dienes, see Section I.2.I.4.2.I.2., and some electrophilic alkenes, see Section I.2.I.4.2.I.8.2. The reason why these catalysts exhibit peculiar properties is not clear,other crown ethers behave like typical phase-transfer catalysts (Table 25). " ... 

Dibenzo-18-crown-6 catalyzed synthesis of pure 1-bromo-l-chlorocyclopropanes is possible within a narrow range of experimental conditions and for a limited number of alkenes only. This is exemplified by the reaction of hex-l-ene to give 7-9. ... 

The synthesis of arsonium ylides 384 from diazocyclopentadienes 383 and tri-phenylarsine has been reexamined with respect to the efficiency of various copper-containing catalysts Whereas copper bronze gave only ca. 55 % of ylide, yields over 80% were provided by the use of Ou(II) complexes of p-diketonates derived from acetylacetone, 3-methylacetylacetone, benzoylacetone or dibenzoylmethane, as well as by bis[4-(phenylimino)-2-pentanonato-N,0-]copper(II) and Cu(II) acetate, all used in boiling benzene. The sterically more demanding complex bis(dipivaloyl-methanato)copper(II) as well as dichlorodipyridinecopper(II) proved less efficient. CopperfTI) tartrate, the dibenzo-14-crown 6/copper complex and furthermore the acetylacetonate complexes of Co, Ni, Pt and Zn were totally ineffective. When 383a was decomposed by Cu(acac)2 in the presence of pyridine or thioanisole. 

In 1967 Charles J. Pedersen, then 2 years away from retirement as a research chemist with Du Pont, published an extensive paper detailing the preparation of 33 cyclic polyethers [1], His thorough investigation of these macrocycles was the culmination of several years work initiated by the accidental preparation of dibenzo[18]crown-6 [2], The compound formed as a result of trace amounts of catechol that had contaminated 2-(hydroxyphenoxy)tetrahydropyran used in the synthesis of the original target compound, bis[2-(hydroxyphenoxy)ethyl]ether. The dibenzocrown ether thus became the first of the crown ethers, as Pedersen called them, to be isolated. 

Reaction of trimethylaluminum with crown ethers - the synthesis and structure of (dibenzo-18-crown-6)bis(trimethylaluminum) and of (15-crown-5)tetrakis(trimethyl-aluminum), J. L. Atwood, D. C. Hrncir, R. Shakir, M. S. Dalton, R. D. Priester and R. D. Rogers, Organometallics, 1982, 1, 1021. 

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