Bromodifluoromethylphosphonium salts. Convenient source of difluorocarbene

Abstract

In recent years considerable attention has been focused on the generation of difluorocarbene for the synthesis of gem-difluorocyclopropanes and other difluoromethylene derivatives. A variety of difluorocarbene precursors have been examined,2 but these

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

“…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

“…[13] For substrates that are thermally unstable, the abovementioned methods and reagents could be a serious limitation, and development of better difluorocarbene precursors that can generate difluorocarbenes at lower temperatures is required. There are only few reports [14] that discuss difluorocarbene generation at room temperature with Ph 3 P/CF 2 Br 2, [15] or at low temperatures (below À78 8C) with bis(trifluoromethyl) cadmium, which is a highly pyrophoric reagent, as a source. Again, the use of cadmium or phosphines and the lack of commercial availability of these reagents is a severe limitation.…”

“…Considering that 1 can serve both as a nucleophilic trifluoromethylating agent [15] and as a difluorocarbene equivalent under different reaction conditions, we envisioned that the reagent might be applied in a one-pot sequential trifluoromethylation and [2+1] cycloaddition reaction. To verify this assumption, we reacted 1 with 4'-(phenylethynyl)-acetophenone (6), which contains both a carbonyl group and a triple bond.…”

Synthetic and mechanistic aspects of the reactions between bromodifluoromethyltriphenylphosphonium bromide and dibromofluoromethyltriphenylphosphonium bromide and trialkylphosphites

“…Bromodifluoromethyltriphenylphosphonium bromide (1) is known to react with potassium fluoride to produce difluorocarbene [8]. Thus, in an attempt to demonstrate that triethylphosphite (2) was capable of intercepting [:CF 2 ], a small scale exploratory reaction between (1), KF, and (2) was carried out in triglyme at room temperature in the presence of an equivalent amount of tetramethylethylene (TME) (Eq.…”