A new zinc difluorocarbenoid reagent

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. Although there are various methods for generation of the less stable, more reactive monofluorocarbene, 51,52 none are as convenient, efficient, or generally useful as those discussed above for difluorocarbene.…”

Trimethylsilyl fluorosulfonyldifluoroacetate (TFDA): a new, highly efficient difluorocarbene reagent

“…After the mixture is heated to 60 8C for 2 h, 2-fluorosulfonyl-2,2-difluoroacetyl chloride is obtained (18.7 g, 95%) by fractionation as a colorless liquid: 13 …”

“…A number of other very nice difluorocarbene reagents have been developed over the years in the hope of discovering a convenient, generally useful, room temperature difluorocyclopropanation procedure [11][12][13]. However, as witnessed by the above examples of ''reactive'' sources of :CF 2 , it has finally been recognized that any generally-useful difluorocarbene reagent must be capable of generating the :CF 2 at a sufficiently high temperature (>80 8C) to overcome the apparently substantial energy barrier for :CF 2 addition to all but the most reactive of alkenes.…”

Synthesis of gem‐Difluorinated Cyclopropanes and Cyclopropenes: Trifluoromethyltrimethylsilane as a Difluorocarbene Source

“…Some of the reagents used previously include sodium chlorodifluoroacetate (or sodium bromodifluoroacetate), [7] PhHgCF 3 [8] and Me 3 SnCF 3 [9] (Seyferth reagents), FSO 2 CF 2 CO 2 SiMe 3 (TFDA), [6h, 10] and Zn/CF 2 Br 2 . [11] However, most of these reagents suffer from disadvantages such as harsh reaction conditions, high toxicity, lack of commercial availability, and/ or low product yields. Recently, Hu and co-workers reported that TMSCF 2 Cl can act as an efficient difluorocarbene precursor under chloride-ion catalysis at 110 8C.…”