Metal-Free Hydrophosphanation of 1-Vinylimidazoles with Secondary Phosphanes: A Straightforward Atom-Economic Route to Tertiary Phosphanes with Imidazolyl Substituents

Abstract

Free radical addition (UV irradiation, 2-7 h or AIBN, 65-70 ˚C, 6-7 h) of secondary phosphanes to 1-vinylimidazole, 2-methyl-1-vinylimidazole, and 1-vinylbenzimidazole proceeds regio­selectively to give the corresponding anti-Markovnikov adducts in 88-98% yields.

Key words

nitrogen heterocycles - 1-vinylimidazoles - secondary phosphanes - radical reactions - phosphane addition

References and Notes

• 1a Kläui W. Piefer C. Rheinwald G. Lang H. Eur. J. Inorg. Chem.  2000,  1549 
• 1b Brauer DJ. Kottsieper KW. Liek C. Stelzer O. Waffenschmidt H. Wasserscheid P. J. Organomet. Chem.  2001,  630:  177 
• 1c Jalil MA. Yamada T. Fujinami S. Hojo T. Nishikawa H. Polyhedron  2001,  20:  627 
• 1d Grotjahn DB. Incarvito CD. Rheingold AL. Angew. Chem. Int. Ed.  2001,  40:  3884 
• 1e Harkal S. Rataboul F. Zapf A. Fuhrmann C. Riermeier T. Monsees A. Beller M. Adv. Synth. Catal.  2004,  346:  1742 
• 1f Grotjahn DB. Gong Y. Zakharov L. Golen JA. Rheingold AL. J. Am. Chem. Soc.  2006,  128:  438 
• 1g Debono N. Canac Y. Duhayon C. Chauvin R. Eur. J. Inorg. Chem.  2008,  2991 
• 1h Canac Y. Debono N. Vendier L. Chauvin R. Inorg. Chem.  2009,  48:  5562 
• 1i Schulz T. Torborg C. Schäffner B. Huang J. Zapf A. Kadyrov R. Börner A. Beller M. Angew. Chem.  2009,  121:  936 
• 1j Field LD. Messerle BA. Vuong KQ. Turner P. Dalton Trans.  2009,  3599 
• 2a Steenken S. Chem. Rev.  1989,  89:  503 
• 2b Parker WB. Chem. Rev.  2009,  109:  2880 
• 3a Grimmett MR. In Comprehensive Heterocyclic Chemistry II   Vol. 3:  Katritzky AR. Rees CW. Scriven EFV. Pergamon; Oxford: 1996.  p.77-220  
• 3b De Luca L. Curr. Med. Chem.  2006,  13:  1 
• 3c Jin Z. Nat. Prod. Rep.  2006,  23:  464 
• 3d Bellina F. Cauteruccio S. Rossi R. Tetrahedron  2007,  63:  4571 
• 4a Tolmachev AA. Yurchenko AA. Semenova MG. Feshchenko NG. Zh. Obshch. Khim.  1993,  63:  714 ; Chem. Abstr. 1993, 119, 180912f
• 4b Tolmachev AA. Yurchenko AA. Merculov AS. Semenova MG. Zarudnitskii EV. Ivanov VV. Pinchuk AM. Heteroat. Chem.  1999,  10:  585 
• 4c Schiller A. Scopelliti R. Benmelouka M. Severin K. Inorg. Chem.  2005,  44:  6482 
• 5a Kottsieper KW. Stelzer O. Wasserscheid P. J. Mol. Catal. A: Chem.  2001,  175:  285 
• 5b Miranda-Soto V. Grotjahn DB. DiPasquale AG. Rheingold AL. J. Am. Chem. Soc.  2008,  130:  13200 
• 6a Trofimov BA. Brandsma L. Arbuzova SN. Malysheva SF. Gusarova NK. Tetrahedron Lett.  1994,  35:  7647 
• 6b Gusarova NK. Malysheva SF. Kuimov VA. Belogorlova NA. Mikhailenko VL. Trofimov BA. Mendeleev Commun.  2008,  18:  260 
• 6c Trofimov BA. Gusarova NK. Mendeleev Commun.  2009,  19:  295 
• 8a Leca D. Fensterbank L. Lacôte E. Malakria M. Chem. Soc. Rev.  2005,  34:  858 
• 8b Coudray L. Montchamp J.-L. Eur. J. Org. Chem.  2008,  3601 
• 8c Trofimov BA. Gusarova NK. Chernysheva NA. Yas’ko SV. Kazantseva TI. Ushakov IA. Synthesis  2008,  2743 
• 9 Jessop CM. Parsons AF. Routledge A. Irvine DJ. Eur. J. Org. Chem.  2006,  1547 

7

General Procedure for the Synthesis of Phosphanes 7a-g
A solution of phosphane 1-3 (1 mmol) and imidazole 4-6 (1 mmol) in dioxane (0.5 mL) was irradiated (200 W Hg arc lamp) in a quartz ampoule (method A) or heated at 65-70 
˚C in the presence of AIBN (1 wt% of the total mass of reactants) in a sealed ampoule (method B; reaction times are given in Table  [¹] ). The reaction was monitored by ^³¹P NMR by disappearance of the signal of the starting phosphanes (δ = -69 to -70 ppm) and appearance of a new signal in the region of δ = -29 to -31 ppm, corresponding to tertiary phosphanes 7a-g. Dioxane was then removed under reduced pressure and the residue was dissolved in hexane (3 mL). The solution was passed through a thin layer of Al₂O₃, and the solvent was evaporated in vacuo to give tertiary phosphanes 7a-g of analytical purity. All manipulations were carried out under argon atmosphere.
Bis(2-phenethyl)-[2-(1 H -imidazolyl)ethyl]phosphane (7a) Anal. Calcd C₂₁H₂₅N₂P: C, 74.98; H, 7.49; N, 8.33; P, 9.21. Found: C, 74.70; H, 7.42; N, 8.13; P, 9.08. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.63-1.83 (m, 6 H, CH₂P), 2.68-2.75 (m, 4 H, CH₂Ph), 3.92-3.98 (m, 2 H, CH₂N), 6.84 and 7.03 (s, 2 H, H^4,5 in imidazole), 7.14-7.29 (m, 10 H, Ph), 7.41 (s, 1 H, H^² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 29.0 (d, ^² J _PC = 13.7 Hz, CH₂Ph), 29.43 (d, ^¹ J _PC = 16.9 Hz, PCH₂CH₂N), 32.28 (d, ^¹ J _PC = 15.0 Hz, CH₂P), 44.70 (d, ^² J _PC = 22.8 Hz, CH₂N), 118.54 (C⁴ in imidazole), 126.27 (p-C in Ph), 128.16 (o-C in Ph), 128.62 (m-C in Ph), 129.67 (C⁵ in imidazole), 136.73 (C^² in imidazole), 142.19 (d, ^³ J _PC = 9.6 Hz, ipso-C in Ph) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = -28.31 ppm.
Bis(2-phenethyl)[2-(2-methyl-1 H -imidazolyl)ethyl]-phosphane (7b) Anal. Calcd C₂₂H₂₇N₂P: C, 75.40; H, 7.77; N, 7.99; P, 8.84. Found: C, 75.65; H, 7.74; N, 7.93; P, 8.81. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.68-1.74 (m, 6 H, PCH₂), 2.32 (s, 3 H, Me), 2.69-2.71 (m, 4 H, CH₂Ph), 3.80-3.88 (m, 2 H, CH₂N), 6.74 and 6.85 (s, 2 H, H^4,5 in imidazole), 7.13-7.21 (m, 10 H, Ph) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 12.85 (Me), 28.75 (d, ^² J _PC = 14.1 Hz, CH₂Ph), 29.46 (d, ^¹ J _PC = 19.1 Hz, PCH₂CH₂N), 32.02 (d, ^¹ J _PC = 14.6 Hz, PCH₂), 43.52 (d, ^² J _PC = 21.8 Hz, CH₂N), 118.57 (C⁴ in imidazole), 126.05
(p-C in Ph), 127.85 (o-C in Ph), 128.15 (C⁵ in imidazole), 128.49 (m-C in Ph), 141.94 (d, ^³ J _PC = 10.9 Hz, ipso-C in Ph), 143.76 (C^² in imidazole) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = -31.15 ppm.
Bis(2-phenethyl)[2-(1 H -1,3-benzimidazolyl)ethyl]-phosphane (7c) Anal. Calcd C₂₅H₂₇N₂P: C, 77.70; H, 7.04; N, 7.25; P, 8.01. Found: C, 77.68; H, 7.06; N, 7.21; P, 8.30. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.65-1.71 (m, 4 H, PCH₂), 1.86-1.89 (m, 2 H, PCH ₂CH₂N), 2.65-2.66 (m, 4 H, CH₂Ph), 4.12-4.17 (m, 2 H, CH₂N), 7.08-7.29 (m, 12 H, Ph, H^5,6 in imidazole), 7.32, 7.81 and 7.83 (m, 3 H, H^4,7,² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 27.70 (d, ^¹ J _PC = 17.1 Hz, PCH₂CH₂N,), 28.76 (d, ^² J _PC = 13.9 Hz, CH₂Ph), 32.0 (d, ^¹ J _PC = 14.3 Hz, PH₂), 42.64 (d, ^² J _PC = 23.4 Hz, CH₂N), 109.40 (C⁷ in imidazole), 120.36 (C⁴ in imidazole), 122.02 (C⁶ in imidazole), 122.76 (C⁵ in imidazole), 126.06 (p-C in Ph), 127.97 (o-C in Ph), 128.60 (m-C in Ph), 133.24 (C⁸ in imidazole), 141.96 (d, ^³ J _PC = 10.9 Hz, ipso-C in Ph), 142.42 (C^² in imidazole), 143.81 (C⁹ in imidazole) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = -30.96 ppm. Bis[2-(4- tert -butylphen)ethyl][2-(1 H -imidazolyl)ethyl]-phosphane (7d) Anal. Calcd C₂₉H₄₁N₂P: C, 77.64; H, 9.21; N, 6.24; P, 6.90. Found: C, 77.66; H, 9.20; N, 6.21; P, 6.76. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.27 (s, 18 H, Me), 1.66-1.77 (m, 6 H, PCH₂), 2.66-2.68 (m, 4 H, CH ₂C₆H₄), 3.94-3.97 (m, 2 H, CH₂N), 6.83 and 7.02 (s, 2 H, H^4,5 in imidazole), 7.08-7.10 and 7.29-7.31 (m, 8 H, C₆H₄), 7.43 (s, 1 H, H^² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 28.90 (d, ^² J _PC = 12.7 Hz, CH₂C₆H₄), 29.43 (d, ^¹ J _PC = 19.4 Hz, P CH₂ CH₂N), 31.47 (Me), 31.76 (d, ^¹ J _PC = 19.6 Hz, CH₂P), 34.50 (C-Me), 44.82 (d, ^² J _PC = 20.3 Hz, CH₂N), 118.62 (C⁴ in imidazole), 125.59 (o-C in C₆H₄), 125.84 (C⁵ in imidazole), 127.87 (m-C in C₆H₄), 136.69 (C^² in imidazole), 139.18 (d, ^³ J _PC = 10.9 Hz, ipso-C in C₆H₄), 149.15 (p-C in C₆H₄) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = -29.80 ppm. Bis[2-(4- tert -butylphen)ethyl][2-(2-methyl-1 H -imidazolyl)ethyl]phosphane (7e) Anal. Calcd C₃₀H₄₃N₂P: C, 77.88; H, 9.37; N, 6.06; P, 6.69. Found: C, 77.67; H, 9.34; N, 6.10; P, 6.63. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.28 (s, 18 H, MeC₆H₄), 1.67-1.75 (m, 6 H, PCH₂), 2.30 (s, 3 H, Me), 2.68-2.70 (m, 4 H, CH ₂C₆H₄), 3.80-3.85 (m, 2 H, CH₂N), 6.75 and 6.80 (s, 2 H, H^4,5 in imidazole), 7.13-7.23 (m, 8 H, C₆H₄) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 13.01 (Me), 28.76 (d, ^² J _PC = 14.3 Hz, CH₂C₆H₄), 29.49 (d, ^¹ J _PC = 18.8 Hz, P CH₂ CH₂N), 31.47 (MeC₆H₄), 32.46 (d, ^¹ J _PC = 14.6 Hz, CH₂P), 34.50 (C-Me), 43.82 (d, ^² J _PC = 22.3 Hz, CH₂N), 118.52 (C⁴ in imidazole), 126.09 (o-C in C₆H₄), 127.53 (C⁵ in imidazole), 127.77
(m-C in C₆H₄), 141.95 (d, ^³ J _PC = 10.7 Hz, ipso-C in C₆H₄), 143.76 (C^² in imidazole), 144.15 (p-C in C₆H₄) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = -31.20 ppm. Bis[2-(4- tert -butylphen)ethyl][2-(1 H -1,3-benzimidazolyl)ethyl]phosphane (7f) Anal. Calcd C₃₃H₄₃N₂P: C, 79.48; H, 8.69; N, 5.62; P, 6.21. Found: C, 79.40; H, 8.61; N, 5.58; P, 6.11. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.28 (s, 18 H, Me), 1.68-1.75 (m, 4 H, CH₂P), 1.93-1.98 (m, 2 H, PCH ₂CH₂N), 2.64-2.71 (m, 4 H, CH ₂C₆H₄), 4.19-4.25 (m, 2 H, CH₂N), 6.81 and 6.98 (m, 2 H, H^5,6 in imidazole), 7.03-7.07 and 7.28-7.31 (m, 9 H, C₆H₄, H⁴ in imidazole), 7.79 and 7.85 (s, 2 H, H^7,² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 27.76 (d, ^¹ J _PC = 17.1 Hz, CH₂ CH₂N), 28.70 (d, ^² J _PC = 13.9 Hz, CH₂C₆H₄), 31.27 (Me), 31.48 (d, ^¹ J _PC = 15.5 Hz, CH₂P), 34.26 (CMe), 42.72 (d, ^² J _PC = 23.1 Hz, CH₂N), 109.41
(C⁷ in imidazole), 120.40 (C⁴ in imidazole), 122.10 (C⁶ in imidazole), 122.86 (C⁵ in imidazole), 125.28 (o-C in C₆H₄), 127.72 (m-C in C₆H₄), 133.26 (C⁸ in imidazole), 138.95 (d, ^³ J _PC = 10.9 Hz, ipso-C in C₆H₄), 142.41 (C^² in imidazole), 143.73 (C⁹ in imidazole), 148.97 (p-C in C₆H₄) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = -31.15 ppm.
Bis(phenhyl)-[2-(1 H -imidazolyl)ethyl]phosphane (7g) Anal. Calcd C₁₇H₁₇N₂P: C, 72.84; H, 6.11; N, 9.99; P, 11.05. Found: C, 72.80; H, 6.12; N, 9.93; P, 11.01. ^¹H NMR (400.13 MHz, CDCl₃): δ = 2.48-2.52 (m, 2 H, CH₂P), 3.96-4.01 (m, 2 H, CH₂N), 6.85 and 7.01 (m, 2 H, H^4,5 in imidazole), 7.31-7.71 (m, 10 H, Ph), 8.67 (s, 1 H, H^² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 30.51 (d, ^¹ J _PC = 14.8 Hz, CH₂ P), 44.13 (d, ^² J _PC = 23.5 Hz, CH₂N), 118.54 (C⁴ in imidazole), 128.89 (d, ^³ J _PC = 13.4 Hz, m-C in Ph), 129.16 (p-C in Ph), 129.57 (C⁵ in imidazole), 130.69 (d, ^² J _PC = 11.4 Hz, o-C in Ph), 132.61 (d, ^¹ J _PC = 19.1 Hz, ipso-C in Ph), 136.77 (C^² in imidazole) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = -20.84 ppm.

10

General Procedure for the Preparation of the Phosphane Oxides 8a-g
A solution of phosphane 7a-g (1 mmol) in acetone was stirred at r.t. under air atmosphere. After reaction completion, as indicated by TLC, the solvent was removed under reduced pressure to afford phosphane oxide 8a-g.
Bis(2-phenethyl)[2-(1 H -imidazolyl)ethyl]phosphane Oxide (8a)
Yield 349 mg (99%), colorless crystalline solid, mp 99-102 ˚C (hexane). Anal. Calcd C₂₁H₂₅N₂OP: C, 71.57; H, 7.15; N, 7.95; P, 8.79. Found: C, 71.47; H, 7.12; N, 7.83; P, 8.71. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.91-2.08 (m, 6 H, CH₂P), 2.83-2.87 (m, 4 H, CH₂Ph), 4.16-4.23 (m, 2 H, CH₂N), 6.86 and 7.03 (s, 2 H, H^4,5 in imidazole), 7.16-7.28 (m, 10 H, Ph), 7.48 (s, 1 H, H^² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 27.55 (d, ^² J _PC = 3.2 Hz, H₂Ph), 30.36 (d, ^¹ J _PC = 60.1 Hz, PCH₂CH₂N), 30.56 (d, ^¹ J _PC = 63.2 Hz, CH₂P), 40.14 (CH₂N), 118.64 (C⁴ in imidazole), 126.68 (p-C in Ph), 128.0 (o-C in Ph), 128.75 (m-C in Ph), 129.60 (C⁵ in imidazole), 136.91 (C^² in imidazole), 140.13 (d, ^³ J _PC = 11.0 Hz, ipso-C in Ph) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = 43.56 ppm.
Bis(2-phenethyl)[2-(2-methyl-1 H -imidazolyl)ethyl]-phosphane Oxide (8b)
Yield 359 mg (98%), light-yellow oil. Anal. Calcd C₂₂H₂₇N₂OP: C, 72.11; H, 7.43; N, 7.64; P, 8.45. Found: C, 72.15; H, 7.44; N, 7.63; P, 8.41. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.94-2.01 (m, 6 H, PCH₂), 2.36 (s, 3 H, Me), 2.83-2.87 (m, 4 H, CH₂Ph), 4.08-4.14 (m, 2 H, CH₂N), 6.78 and 6.87 (s, 2 H, H^4,5 in imidazole), 7.13-7.21 (m, 10 H, Ph) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 12.85 (Me), 27.51 (CH₂Ph), 29.62 (d, ^¹ J _PC = 60.2 Hz, PCH₂CH₂N), 30.49 (d, ^¹ J _PC = 63.5 Hz, CH₂P), 38.99 (CH₂N), 118.71 (C⁴ in imidazole), 126.52 (p-C in Ph), 127.93 (o-C in Ph), 128.55 (C⁵ in imidazole), 128.83 (m-C in Ph), 140.07 (d, ^³ J _PC = 11.8 Hz, ipso-C in Ph), 144.12 (C^² in imidazole) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = 45.31 ppm.
Bis(2-phenethyl)[2-(1 H -1,3-benzimidazolyl)ethyl]-phosphane Oxide (8c)
Yield 398 mg (99%), colorless crystalline solid, mp 190-200 ˚C (hexane). Anal. Calcd C₂₅H₂₇N₂OP: C, 74.61; H, 6.76; N, 6.96; P, 7.70. Found: C, 74.67; H, 6.56; N, 6.87; P, 7.75. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.85-1.92 (m, 4 H, PCH₂), 2.11-2.17 (m, 2 H, PCH ₂CH₂N), 2.74-2.79 (m, 4 H, CH₂Ph), 4.41-4.48 (m, 2 H, CH₂N), 7.03-7.27 (m, 12 H, Ph, H^5,6 in imidazole), 7.35 (s, 1 H, H⁴ in imidazole), 7.76 and 7.92 (m, 2 H, H^7,² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 27.55 (CH₂Ph), 28.36 (d, ^² J _PC = 60.0 Hz, PCH₂CH₂N), 30.67 (d, ^¹ J _PC = 62.0 Hz, CH₂P), 38.26 (CH₂N), 109.41 (C⁷ in imidazole), 120.52 (C⁴ in imidazole), 122.48 (C⁶ in imidazole), 123.27 (C⁵ in imidazole), 126.64 (p-C in Ph), 127.96 (o-C in Ph), 128.72 (m-C in Ph), 132.99 (C⁸ in imidazole), 140.04 (d, ^³ J _PC = 12.5 Hz, ipso-C in Ph), 142.93 and 143.65 (C^²,9 in imidazole) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = 43.95 ppm.
Bis[2-(4- tert -butylphen)ethyl][2-(1 H -imidazolyl)ethyl]-phosphane Oxide (8d)
Yield 455 mg (98%), colorless crystalline solid, mp 140-141 ˚C (hexane). Anal. Calcd C₂₉H₄₁N₂OP: C, 74.97; H, 8.89; N, 6.03; P, 6.67. Found: C, 74.86; H, 8.95; N, 6.21; P, 6.76. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.29 (s, 18 H, Me), 1.95-2.06 (m, 6 H, PCH₂), 2.71-2.83 (m, 4 H, CH₂Ph), 4.20-4.22 (m, 2 H, CH₂N), 6.84 (s, 1 H, H⁴ in imidazole), 7.04-7.32 (m, 9 H, C₆H₄, H⁵ in imidazole), 7.46 (s, H^² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 27.11 (CH₂Ph), 30.47 (d, ^¹ J _PC = 60.7 Hz, P CH₂ CH₂N), 30.54 (d, ^¹ J _PC = 62.7 Hz, CH₂P), 31.29 (Me), 34.40 (CMe), 40.26 (CH₂N), 118.69 (C⁴ in imidazole), 125.67 (o-C in C₆H₄), 127.73 (m-C in C₆H₄), 129.66 (C⁵ in imidazole), 136.93 (d, ^³ J _PC = 12.6 Hz, ipso-C in Ph), 149.23 and 149.82 (C^² in imidazole and p-C in C₆H₄) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = 44.86 ppm.
Bis[2-(4- tert -butylphen)ethyl][2-(2-methyl-1 H -imidazolyl)ethyl]phosphane Oxide (8e)
Yield 464 mg (97%), colorless crystalline solid, mp 134-136 ˚C (hexane). Anal. Calcd C₃₀H₄₃N₂OP: C, 75.28; H, 8.05; N, 5.85; P, 6.47. Found: C, 75.36; H, 8.25; N, 6.01; P, 6.56. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.28 (s, 18 H, Me), 1.94-2.05 (m, 6 H, CH₂P), 2.41 (s, 3 H, Me in imidazole), 2.82-2.84 (m, 4 H, CH ₂C₆H₄), 4.11-4.18 (m, 2 H, CH₂N), 6.76 and 6.91 (s, 2 H, H^4,5 in imidazole), 7.07-7.10 and 7.25-7.32 (m, 8 H, C₆H₄) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 12.95 (Me in imidazole), 27.25 (d, ^² J _PC = 3.0 Hz, CH₂C₆H₄), 29.82 (d, ^¹ J _PC = 61.9 Hz, P CH₂ CH₂N), 30.62 (d, ^¹ J _PC = 64.1 Hz, CH₂P), 31.44 (Me), 34.53 (CMe), 39.45 (CH₂N), 118.89 (C⁴ in imidazole), 125.85 (o-C in C₆H₄), 127.22 (C⁵ in imidazole), 127.80 (m-C in C₆H₄), 137.13 (d, ^³ J _PC = 12.8 Hz, ipso-C in C₆H₄), 144,38 (C^² in imidazole), 149.80 (p-C in C₆H₄) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = 44.74 ppm.
Bis[2-(4- tert -butylphen)ethyl][2-(1 H -1,3-benzimidazolyl)-ethyl]phosphane Oxide (8f)
Yield 509 mg (99%); light-yellow oil. Anal. Calcd C₃₃H₄₃N₂OP: C, 77.01; H, 8.42; N, 5.44; P, 6.02. Found: C, 77.17; H, 8.50; N, 5.73; P, 6.11. ^¹H NMR (400.13 MHz, CDCl₃): δ = 1.25 (s, 18 H, Me), 1.88-2.03 (m, 4 H, CH₂P), 2.14-2.18 (m, 2 H, PCH ₂CH₂N), 2.76-2.78 (m, 4 H, CH₂Ph), 4.45-4.51 (m, 2 H, CH₂N), 6.98 and 7.01 (s, 2 H, H^5,6 in imidazole), 7.24-7.34 (m, 8 H, C₆H₄), 7.39 (s, 1 H, H⁴ in imidazole), 7.78 (s, 1 H, H⁷ in imidazole), 7.91 (s, 1 H, H^² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 27.13 (CH₂Ph), 28.54 (d, ^¹ J _PC = 60.0 Hz, P CH₂ CH₂N), 30.65 (d, ^¹ J _PC = 62.6 Hz, CH₂P), 31.26 (Me), 34.33 (CMe), 38.30 (CH₂N), 109.35 (C⁷ in imidazole), 120.60 (C⁴ in imidazole), 122.49 (C⁶ in imidazole), 123.29 (C⁵ in imidazole), 125.61 (o-C in C₆H₄), 127.63 (m-C in C₆H₄), 134.91 (C⁸ in imidazole), 136.94 (d, ^³ J _PC = 11.4 Hz, ipso-C in C₆H₄), 142.83 (C^² in imidazole), 143.72 (C⁹ in imidazole), 149.61 (p-C in C₆H₄) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = 44.83 ppm.
Bis(phenyl)-[2-(1 H -imidazolyl)ethyl]phosphane Oxide (8g)
Yield 287 mg (97%), colorless crystalline solid, mp 38-39 ˚C (hexane). Anal. Calcd C₁₇H₁₇N₂OP: C, 68.91; H, 5.78; N, 9.45; P, 10.45. Found: C, 68.89; H, 5.77; N, 9.43; P, 10.41. ^¹H NMR (400.13 MHz, CDCl₃): δ = 2.77-2.78 (m, 2 H, CH₂P), 4.28-4.30 (m, 2 H, CH₂N), 6.88 and 6.93 (s, 2 H, H^4,5 in imidazole), 7.27-7.70 (m, 10 H, Ph), 8.04 (s, 1 H, H^² in imidazole) ppm. ^¹³C NMR (100.62 MHz, CDCl₃): δ = 32.15 (d, ^¹ J _PC = 67.7 Hz, CH₂ P), 40.43 (CH₂N), 118.69 (C⁴ in imidazole), 128.91 (d, ^³ J _PC = 12.3 Hz, m-C in Ph), 129.96 (C⁵ in imidazole), 130.47 (d, ^² J _PC = 9.5 Hz, o-C in Ph), 131.56 (d, ^¹ J _PC = 100.3 Hz, ipso-C in Ph), 136.77 (C^² in imidazole) ppm. ^³¹P NMR (161.98 MHz, CDCl₃): δ = 29.46 ppm.