EPR study of spin adducts of silyl and phosphonyl radicals with higher internal perfluoroalkenes

Fluoroalkenylphosphonates from branched chain and cyclic perfluoroolefins

“…But the synthesis of fluoroalkenylphosphonates could be achieved by adding dialkyl phosphites followed by dehydrofluorination [14]. We have previously shown that dialkyl phosphites selectively add to compound 8 under radical conditions [15,16]. The exclusive formation of one stereoisomer of dialkyl 4,4,4,3,2,1-hexafluoro-3,4-bis(trifluoromethyl)butylphosphonates (9a and b) can be explained as follows.…”

“…The exclusive formation of one stereoisomer of dialkyl 4,4,4,3,2,1-hexafluoro-3,4-bis(trifluoromethyl)butylphosphonates (9a and b) can be explained as follows. Firstly, as we earlier assumed, the radical centre (A) has a planar structure; this assumption was made from the results of studying the intermediate radicals by ESR and by molecular mechanics [15,16]. Secondly, the mobility of the substituents at the radical centre in branched perfluorinated radicals is limited [17], probably because of the high energetic rotation barrier of the bulky substituents [(CF 3 Treatment of phosphonate (9a) with BF 3 ÁNEt 3 led to a 1:1 mixture of the fluoroalkenylphosphonates (10) and (11).…”