Catechols cyclic carbonates

Cyclic carbonates have been used to a limited extent only (since they are readily hydrolyzed) to protect the catechol group in a polyhydroxy benzene. 

Polycarbonates were first prepared by Einhom in 1898 by reacting the dihydroxybenzenes, hydroquinone and resorcinol, separately with phosgene in solution in pyridine. The hydroquinone polycarbonate was an infusible and insoluble crystalline power whereas the resorcinol polymer was an amorphous material melting at about 200°C. The third dihydroxybenzene, catechol, yields a cyclic carbonate only, which is not surprising bearing in mind the proximity of... 

With hydrohalic acids as catalysts, the hydrolysis of 1,3,2-dioxathiolane 2-oxide (16) is considered to occur (partly or entirely) via a halosulfite intermediate, e.g. (138 X = C1). The marked acceleration of the aqueous hydrolysis of catechol cyclic sulfite by small amounts of fluoride ion is likewise attributed to a nucleophilic catalysis (76CRV747). The nucleophilic attack of (16) at carbon by halide ion on reaction with phenylmagnesium bromide has already been discussed in Section 4.33.3.3.4. 

Cyclic carbonates. For conversion of catechol into phenylenecarbonate, " 1 mole of the phenol li dlisolved under nitrogen in a deaerated solution of 2.2 moles of, 011... 

Catechol is readily converted into a cyclic carbonate using two molar equivalents of phosgene in the presence of a sodium hydroxide solution [879a] ... 

CO2. 132) The principal complications of this reaction are very low rates and the formation of substantial amounts of cyclic carbonates as byproducts. An interesting class of catalysts based on adducts of di- and triphenols to (hethylzinc, developed by Kuran, (133,134) is reported to have a rate and selectivity which increase with CO2 concentration, suggesting that both can be improved by operating in supercridcal CO2 instead of the usu5 solvent, dioxane. TTie highest selectivity in dioxane is reported for the 3 2 diethylzinc catechol adduct... 

Early developments in aliphatic and aromatic polycarbonates. The first significant documentation of aromatic polycarbonates synthesis began with Einhom [24]. He reacted hydroquinone, resorcinol, and catechol with phosgene in a pyridine solution, obtaining linear polymers from hydroquinone (an insoluble crystalline powder that melted above 280°C) and resorcinol (an amorphous material that melted with decomposition at 190 to 200°C), and a cyclic carbonate from catechol. Subsequent research was focused on finding more efficient preparation methods and on improving material properties [25]. 

The smallest possible five-membered aromatic cyclic carbonate is a derivative of catechol benzo-l,3-dioxolan-2-one (o-phenylene carbonate) (1, Scheme 13). It was synthesized using three different methods the reaction of catechol with phosgene (or its dimer or trimer), ° the reaction of catechol with chloroformate, ° or by transesterification of catechol with diphenyl carbonate. ... 

Catechols can be protected as diethers or diesters by methods that have been described to protect phenols. However, formation of cyclic acetals and ketals (e.g., methylenedioxy, acetonide, cyclohexylidenedioxy, diphenylmethylenedioxy derivatives) or cyclic esters (e.g., borates or carbonates) selectively protects the two adjacent hydroxyl groups in the presence of isolated phenol groups. 

The conditions for reliable cyclic voltametry determination of trace Sn concentrations in sea water were investigated. All organotin compounds should be converted to Sn(II) by UV-photolysis adsorption on mercury drop in the presence of 40 pM of tropolone (1) cyclic voltametry stripping shows two cathodic peaks, corresponding to the two-step process Sn(IV) — Sn(II) -> Sn(0)29. A complex of Sn ions with catechol can be accumulated in a glassy carbon mercury film electrode, followed by stripping voltametry measurement in the cathodic direction, at pH 4.2-4.7. Interference occurs when Cu, Cd and Cr are present LOD 0.5 pg/L for 300 s accumulation30. 

The Claisen rearrangement has attracted much attention as an attractive tool for the construction of new carbon-carbon bonds. Taguchi et al. reported the enantioselective and regioselective aromatic Claisen rearrangement of catechol mono allylic ether derivatives by means of Corey s chiral boron reagent (Eq. 70) [53a,54]. The mechanism of enantioselectivity is that a rigid five-membered cyclic intermediate is formed by reaction of catechol mono allylic ethers with the chiral boron reagent and this is fol-... 

---