The reaction of 2,5-diphenylphosphacymantrene with solid KOH in the presence of crown ethers: Synthesis of the anionic η4-phosphoryl manganese complexes

One-step synthesis of dimethyl carbonate from carbon dioxide, propylene oxide and methanol over alkali halides promoted by crown ethers

“…Unfortunately, the solubility of alkali halides is quite low in organic solvents (e.g., the solubility of KCl is less than 0.5 g/100 g in methanol at room temperature), which leads to lower interface between catalysts and reactants and, as a consequence, lower catalytic performance. It is well known that crown ethers and alkali halides can form an organometallic complex due to the good complexing ability between crown ethers and alkali metal ions [30,31]. This complexation is not only beneficial to solution of alkali halides in reactant system, but it also promotes more "bare anions" used as free nucleophilic groups, which will increase the probability of the nucleophilic reaction (i.e., the first step cycloaddition reaction of one-step synthesis of DMC, as shown in Scheme 1) [16] and, as a consequence, high yield of DMC.…”

“…1a, d), which may be leads to lower interface between catalysts and reactants, as a consequence, lower catalytic performance. It is well known that crown ethers and alkali halides can form an organometallic complex due to the good complexing ability between crown ethers and alkali metal ions [30,31], and this complexation is beneficial to solution of alkali halides in the reactant system. Accordingly [2,4],-dibenzo-18-crown-6 (DBC) was added into the reactant system, and the results show that there is little undissolved KCl after reaction (Fig 1b, e), and the DMC yield increases noticeably and reaches 23% (entry 2, Table 1), an increase of 195% compared with KCl alone as catalyst.…”