NMR Studies and electrophilic properties of triphenylphosphine–trifluoromethanesulfonic anhydride; a remarkable dehydrating reagent system for the conversion of aldoximes into nitriles

An Approach to P=N Bond Formation: Straightforward Synthesis of Arylurea‐Derived Phosphazenes via Condensation of Ph3P=O with N‐Monosubstituted Arylureas

“…of Hendrickson's reagent was employed, no further yield improvement was observed (Table , Entry 14). More importantly, when Ph 3 P was used instead of Ph 3 P=O, 32% yield of 3 a was obtained, suggesting that Ph 3 P and Tf 2 O form a reagent in situ similar to Hendrickson's reagent (Table , Entry 15) . Moreover, when only Ph 3 P, was used, no reactivity was observed (Table , Entry 16).…”

“…Next, the scope of other electron‐withdrawing groups (COOH, CONH 2 ) was investigated. Different N ‐monosubstituted arylurea 2 i ‐ 2 k reacted smoothly to provide access to structurally diverse ArNHC(O)N=PPh 3 products in good to high yields; however, the amide substituent underwent dehydration to form cyanide groups . In the case of electron‐donating groups (Me, i‐Pr, tert‐butyl, OH, OEt), the corresponding products 3 l ‐ 3 q were generated in 71–83% yields.…”

Air- and water-stable Lewis acids: synthesis and reactivity of P-trifluoromethyl electrophilic phosphonium cations

“…5-(Trifluoromethyl)dibenzothiophenium trifluoromethanesulfonate (Umemoto's reagent), 1-Trifluoromethyl-1,2-benziodoxol-3-(1H)-one (Togni's reagent), sodium triflinate (Langlois reagent), Ph 3 P, Ph 2 POPh, TMSCF 3 , CsF and all the reagents for the catalysis screening were purchased from commercial sources and used as received unless otherwise stated. Tris(pentafluorophenyl)fluorophosphonium tetrakis(pentafluorophenyl)borate [(C 6 F 5 ) 3 PF][BArF], 1 triphenylphosphonium anhydride trifluoromethane sulfonate (Hendrickson reagent) 2 and [K][BArF] 3 were synthesized in accordance with the literature. Dichloromethane, d 2 -dichloromethane, d-chloroform were dried over CaH 2 and distilled and degassed before use.…”

“…After inverting the reaction mixture at R.T. for 18 hours, (C 6 F 5 ) 3 PF 2 was observed; the high fluorophilicity of the starting phosphonium sequestered the fluoride preventing TMSCF 3 activation, while in absence of CsF no reaction was observed at R.T.). Diagnostic peaks: 31 P{ 1 H} NMR δ = -48.1 ppm (t, 1 J P-F = 695 Hz) and 19 2 : Under inert atmosphere, in a vial Ph 3 PO (45 mg, 0.16 mmol, 2.0 eq.) was dissolved in anhydrous DCM (0.5 mL), followed by the addition of Tf 2 O (14 µL, 0.08 mmol, 1.0 eq.).…”

Hendrickson Reagent (Triphenylphosphonium Anhydride Trifluoromethane Sulfonate)

“…It has successfully been employed in ester, ether and amide formation as well as in the rapid conversion of aldoximes into nitriles, to yield a variety of alkyl and aryl aldoximes. [2][3][4] These reactions occur in a manner that is analogous to the Mitsunobu reaction, involving an intermediate alkoxyphosphonium salt. 5,6 The advantages of the Hendrickson reagent over the Mitsunobu reagent are that the recovered triphenylphosphine oxide may be recycled by treatment with trifluromethanesulfonic anhydride, the use of explosive azodicarboxylates is not required and competing side reactions are avoided.…”