Reactivity and Product Selectivity of Fluoroalkyl Carbonates in Substitution Reactions with Primary Alcohols and Amines.

The present study reports a systematic investigation of the substitution reactions of a series of symmetric and unsymmetric fluoroalkyl carbonates with primary alcohols or amines. The reactivity of the haloalkyl carbonate depends mainly on the electrophilicity and steric crowdedness of the carbonyl group and the leaving ability of the haloalkyl alcohols. Diethyl carbonate as a reference substrate showed no reaction with the alcohol or amine. However, bis(2,2,2-trifluoroethyl) carbonate [(F3-EtO)2CO] having electron-withdrawing trifluoroethyl groups enabled substitution reactions, with relatively higher reactivities to those for diphenyl carbonate [(PhO)2CO]. Furthermore, (F6-iPrO)2CO, bearing two sets of hexafluoroisopropyl groups, showed dramatic acceleration of the reactions, in which the observed reactivities were similar to those for bis(perfluorophenyl) carbonate [(F5-PhO)2CO]. The electrophilicity of the carbonyl group and the leaving ability of the alcohols in the series of haloalkyl carbonates were found to be correlated with the wavenumbers of their carbonyl groups in IR spectra and pKa for the eliminated alcohols, respectively. Since the eliminated fluoroalkyl alcohols exhibit weak affinity with the organic products and have lower boiling points owing to a characteristic property of the fluoroalkyl group, they could be readily removed from the product by simple evaporation below 100 °C with or without reduced pressure.

Photo-on-Demand Base-Catalyzed Phosgenation Reactions with Chloroform: Synthesis of Arylcarbonate and Halocarbonate Esters.

Carbonate esters are utilized as solvents and reagents for C1 building blocks in organic synthesis. This study reports a novel photo-on-demand in situ synthesis of carbonate esters with CHCl3 solutions containing a mixture of an aromatic or haloalkyl alcohol having relatively high acidity, and an organic base. We found that the acid-base interaction of the alcohol and base in the CHCl3 solution plays a key role in enabling the photochemical reaction. This reaction allows practical syntheses of diphenyl carbonate derivatives, haloalkyl carbonates, and polycarbonates, which are important chemicals and materials in industry.