Magnesium iodide promoted defluorinative reactions of 2,2-difluorocyclopropyl aryl ketones with aryl imines: A new, general synthesis of 2-alkylideneazetidines

Dehydrative Ring‐Opening of gem‐Difluorocyclopropyl Carbinols to Allylic Trifluoromethyl and Difluorohalomethyl Derivatives Promated by Titanium Tetrahalide

“…The same group also reported that the treatment of gem ‐difluorocyclopropyl ketones with nitriles in the presence of triflic acid afforded 2‐fluoropyrroles . In addition, MgI 2 strong bases, thiol nucleophiles, and the N ‐pentylpyridinium bromide/triflic acid system showed substantial abilities to promote the ring‐opening of gem ‐difluorocyclopropyl ketones. Recently, the synthesis of 3‐fluorofurans from the gem ‐difluorocyclopropyl ketones was realized with two equivalents of triflic acid …”

The preparation and properties of 1,1-difluorocyclopropane derivatives

“…Dolbier et al also studied the MgI 2 -facilitated reactions of aryl-2,2-difluorocyclopropyl ketones 113 with imines 115 , which led to alkylideneazetidines 116 ( Scheme 52 ) [ 102 ]. The MgI 2 acted as a Lewis acid and reducing agent, effecting the distal C–C bond cleavage in 113a to form an allenyl ketone, or an equivalent fluoro,iodo-enone species, either of which could then have added to the imine 115 and led to the observed product.…”

Friedel−Crafts Reactions of 2,2-Difluorocyclopropanecarbonyl Chloride: Unexpected Ring-Opening Chemistry

“…In conclusion, the FriedelÀCrafts reactions of 2,2-difluorocyclopropanecarbonyl chloride (1) with various arenes did not lead to the straightforward formation of the expected aryl 2,2-difluorocyclopropyl ketones (3). Instead the reactions proceeded, to various degrees depending on the reactivity of the arene, via an apparent rearrangement of the initially formed acylium ion to form novel aryl 3-chloro-3,3-difluoropropyl ketones (2). The formation of the ringopened product 2 was exclusive, and therefore could be synthetically useful, when relatively unreactive arene substrates such as benzene, toluene, and p-xylene are used, and when the reactions are run under dilute conditions with only 1 equiv of arene being used.…”

“…1 Two studies of reactions of 2,2-difluorocyclopropyl ketones that resulted in ring-opening were recently published. One was our study of the MgI 2 -facilitated reactions of aryl 2,2-difluorocyclopropyl ketones with imines, 2 which led to products completely devoid of fluorine, and the second was of their ionic-liquid facilitated ring-opening by HBr. Examples of each of these reactions are given in Scheme 1.…”