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

Abstract

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 pK a 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 In Situ One-Pot Synthesis of Carbonate Esters from Tetrachloroethylene

“…However, no notable product was observed in the reaction by decreasing the ratio of base at [TOA] < [TFE], which allows the increasing vaporization of TFE (entry 8) ( vide infra ). With the same conditions as entry, 7, 2,2,2-trichloroethanol (p K a = 12.2) also provided the corresponding TCAE/carbonate in 68/23% yields (entry 9). PhOH, an aryl alcohol (p K a = 10.0), provided TCAE/carbonate in 58/22% yields (entry 10).…”

“…1 H and 13 C NMR spectra were recorded on a Bruker AVANCE 400 spectrometer or Bruker AVANCE 500 spectrometer, where chemical shifts (δ in ppm) were determined with respect to tetramethylsilane as an internal standard. 19 F NMR spectra were recorded on a Bruker AVANCE 400 spectrometer, where chemical shifts (δ in ppm) were determined with respect to hexafluorobenzene as an external standard. Fourier transform infrared (FT-IR) spectroscopy was recorded on a JASCO FT/IR 4700 equipped with ATR PR0450-S, and samples were loaded neat.…”

In situ photo-on-demand phosgenation reactions with chloroform for syntheses of polycarbonates and polyurethanes

“…To ensure safe use of this reaction, we then developed "in situ" photo-ondemand phosgenation reactions, which required the design and construction of batch and flow reaction systems [25][26][27][28][29][30][31][32][33][34]. We have successfully applied this photo-ondemand phosgenation reaction on a practical scale for most common phosgenation reactions, such as the syntheses of chloroformates [25,26], carbonate esters [28,29], PCs [28], isocyanates [30], Vilsmeier reagents [27], acyl chlorides [25], and α-amino acid N-carboxyanhydrides (NCAs) [32] (Fig. 3).…”