Regioselective functionalization of iminophosphoranes through Pd-mediated C–H bond activation: C–C and C–X bond formation

Abstract

The orthopalladation of iminophosphoranes [R(3)P=N-C(10)H(7)-1] (R(3) = Ph(3) 1, p-Tol(3) 2, PhMe(2) 3, Ph(2)Me 4, N-C(10)H(7)-1 = 1-naphthyl) has been studied. It occurs regioselectively at the aryl ring bonded to the P atom in 1 and 2, giving endo-[Pd(μ-Cl)(C(6)H(4)-(PPh(2=N-1-C(10)H(7))-2)-κ-C,N](2) (5) or endo-[Pd(μ-Cl)(C(6)H(3)-(P(p-Tol)(2)=N-C(10)H(7)-1)-2-Me-5)-κ-C,N](2) (6), while in 3 the 1-naphthyl group is metallated instead, giving exo-[Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7). In the case of 4, orthopalladation at room temperature affords the kinetic exo isomer [Pd(μ-Cl)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (11exo), while a mixture of 11exo and the thermodynamic endo isomer [Pd(μ-Cl)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (11endo) is obtained in refluxing toluene. The heating in toluene of the acetate bridge dimer [Pd(μ-OAc)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (13exo) promotes the facile transformation of the exo isomer into the endo isomer [Pd(μ-OAc)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (13endo), confirming that the exo isomers are formed under kinetic control. Reactions of the orthometallated complexes have led to functionalized molecules. The stoichiometric reactions of the orthometallated complexes [Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7), [Pd(μ-Cl)(C(6)H(4)-(PPh(2)[=NPh)-2)](2) (17) and [Pd(μ-Cl)(C(6)H(3)-(C(O)N=PPh(3))-2-OMe-4)](2) (18) with I(2) or with CO results in the synthesis of the ortho-halogenated compounds [PhMe(2)P=N-C(10)H(6)-I-8] (19), [I-C(6)H(4)-(PPh(2)=NPh)-2] (21) and [Ph(3)P=NC(O)C(6)H(3)-I-2-OMe-5] (23) or the heterocycles [C(10)H(6)-(N=PPhMe(2))-1-(C(O))-8]Cl (20), [C(6)H(5)-(N=PPh(2)-C(6)H(4)-C(O)-2]ClO(4) (22) and [C(6)H(3)-(C(O)-1,2-N-PPh(3))-OMe-4]Cl (24).

Synthesis and Reactivity of Neutral Palladium(II) Alkyl Complexes that Contain Phosphinimine-Arenesulfonate Ligands

“…1 H NMR (THF/benzene-d 6 ): δ 7.71 (s, 1H, 6-CH of −C 6 H 3 SO 3 −), 7.71 (broad, 2H, 2,6-CH of PhPN),7.59 (m, 4-CH of PhPN), 7.07 (broad, 2H, 3,5-CH of PhPN), 6.52 (bd, J = 8.0, 1H, 4-CH of −C 6 H 3 SO 3 −), 6.29 (bd, J = 8.0, 1H, 4-CH of −C 6 H 3 SO 3 −), 2.20−2.50 (m, 4H, CH 2 CH 2 CH 2 CH 3 ), 1.94(s, 3H, 5-CH 3 of −C 6 H 3 SO 3 ), 1.45(m, 4H, CH 2 CH 2 CH 2 CH 3 ), 1.32(m, 4H, CH 2 CH 2 CH 2 CH 3 ), 0.63 (t, J = 7.6, 6H, CH 2 CH 2 CH 2 CH 3 ). 31 2-(( n Bu) 3 PN)-5-MeC 6 H 3 SO 3 Na (3d). To a flask loaded with 1d (1.58 g, 3.68 mmol) and NaH (0.32 g, 5.52 mmol) was added THF (50 mL) while stirring.…”

“…1 H NMR (THF-d 8 ): δ 7.85 (m, 4H, 2, 6-CH of Ph 2 PN),7.67 (s, 1H, 6-CH of −C 6 H 3 SO 3 −), 7.20−7.41 (m, 6H, 3,4,5-CH of Ph 2 PN), 6.44 (d, J = 8.0, 1H, 4-CH of −C 6 H 3 SO 3 −), 6.20 (d, J = 8.0, 1H, 4-CH of −C 6 H 3 SO 3 −), 2.19 (d, J = 13.2, 3H, MePN), 2.00 (s, 3H, 5-CH 3 of −C 6 H 3 SO 3 ). 31 ,4.70;N,3.44. Found: C,58.76;H,4.44;N,3.06. 2-(( n Bu) 2 PhPN)-5-MeC 6 H 3 SO 3 Na (3c).…”

“…13 C NMR (THF-d 8 ):146.4 (2-C), 138.0 (d, J PC = 22.0, 1-C), 133.0 (d, J PC = 9.9, ortho-CH of (C 6 H 5 ) 3 PN−), 132.0 (d, J PC = 98.7, ipso C of (C 6 H 5 ) 3 PN), 130.8 (para-CH of (C 6 H 5 ) 3 PN−), 129.6 (overlapping of 4-and 6-C), 128.2 (d, J PC = 12.2, meta-CH of (C 6 H 5 ) 3 PN−), 123.9 (5-C), 122.0 (3-C), 19.7 (5-CH 3 ). 31 2-(CH 3 (C 6 H 5 ) 2 PN)-5-MeC 6 H 3 SO 3 Na (3b). To a flask loaded with 1b (1.00 g, 2.60 mmol) and NaH (94 mg, 3.90 mmol) was added THF (50 mL) while stirring.…”

“…Filtration of the precipitate, followed by diethyl ether washes (3 × 20 mL), afforded 1c (1.54g, 23%) as a white powder. 1 H NMR (CDCl 3 ): δ 9.51 (d, J = 9.6, 1H, NH), 7.95 (m, 2H, 2,6-CH of n Bu 2 C 6 H 5 P), 7.81 (s, 1H, 6-CH of −C 6 H 3 SO−), 7.72 (m, 1H, 4-CH of n Bu 2 C 6 H 5 P), 6.86 6.86(dd, J = 8.0, 1.2, 1H, 4-CH of −C 6 H 3 SO 3 −), 6.36 (d, J = 8.0, 1H, 3-CH of −C 6 H 3 SO 3 −), 2.69 (m, 2H, CH 2 CH 2 CH 2 CH 3 ), 2.59 (m, 2H, CH 2 CH 2 CH 2 CH 3 ), 2.20 (s, 3H, 5-CH 3 of −C 6 H 3 SO 3 −), 1.59 (m, 4H, CH 2 CH 2 CH 2 CH 3 ), 1.39 (m, 4H, CH 2 CH 2 CH 2 CH 3 ), 0.82 (t, J = 7.2, 6H, CH 2 CH 2 CH 2 CH 3 ), 31 2-(( n Bu) 3 PNH)-5-MeC 6 H 3 SO 3 (1d). To a 200 mL pear-shaped flask containing a clear brown solution of 2 (2.95 g, 11.4 mmol) in toluene (10 mL) chilled to 0°C for 15 min was added a solution of P( n Bu) 3 (2.42 g, 12.0 mmol) in toluene (30 mL) via cannula transfer by aid of rinsing with toluene (10 mL), resulting in a yellow solution.…”

“…27 The accepted mechanism for this reaction is electrophilic substitution and thus may be catalyzed by the presence of an electrophilic palladium center that has increased Lewis acidity after homolysis of the Pd−Me bond of 5a. 30 The 31 P{ 1 H} NMR spectrum of 6a shows a signal at 47 ppm (CD 2 Cl 2 ). This downfield shift is due to strain on phosphorus caused by the 5-membered ring in 6a, which is characteristic of orthopalladated phosphinimines.…”