Synthesis of novel bis- and oligo-gem-difluorocyclopropanes

NHC-catalyzed generation of difluorocarbene and its application to difluoromethylation of oxygen nucleophiles

“…This reagent releases difluorocarbene in the presence of a fluoride ion (F -, 1-2 mol%), which is presumed to attack the Si atom of TFDA to promote decomposition (Scheme 2). The generated difluorocarbene is employed in difluorocyclopropanation of alkenes [18,19], alkynes [20], and allenes [21,22].…”

“…Electron-donating and -withdrawing group on the N-aryl groups did not affect the reaction (Entries 5-8). Although some amount of the imidates decomposed during purification by column chromatography, 19 F NMR analysis suggested that substituted anilides 7e-h gave 8e-h in 69-83% yield. It must be emphasized that the undesired N-difluoromethylated products were not observed by the 19 F NMR analysis of the crude mixtures.…”

“…Indan-1-one 1a was selected as a model substrate for O-difluoromethylation and treated with TFDA (2 equiv) in the presence of 1 to 10 mol% of activators for TFDA. The yields of the produced enol ether 2a and the undesired overreaction product difluorocyclopropane 3 were determined by 19 F NMR spectroscopy. The results of our examination on the activators are summarized in Table 1.…”

“…NMR spectra were recorded on Bruker Avance 500, Bruker AV600, or Bruker AV400 spectrometers in CDCl 3 , at 500, 600, or 400 MHz ( 1 H NMR), at 126, 150, or 100 MHz ( 13 C NMR), and at 470, 565, or 372 MHz ( 19 F NMR). Chemical shift values were given in ppm relative to internal Me 4 Si (for 1 H NMR: δ = 0.00), CDCl 3 (for 13 77.0), and C 6 F 6 (for 19 F NMR: δ = 0.0) [32]. Mass spectra were taken with JMS-T100GCV spectrometer.…”

Structure, Synthesis, and Chemical Reactions of Fluorinated Cyclopropanes and Cyclopropenes

“…46,47 For additions of :CF 2 to electron-rich alkenes, that is alkenes bearing at least three alkyl substituents or more strongly donating groups such as alkoxy or phenyl, there are a number of convenient, roomtemperature methods available, perhaps the best two being those utilizing the precursors introduced by Burton (Ph 3 P/CF 2 Br 2 ) and Dolbier (Zn/CF 2 Br 2 ). [48][49][50] Fluorocarbene.…”