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

Boris A. Trofimov; Svetlana F. Malysheva; Lidiya N. Parshina; Nina K. Gusarova; Nataliya A. Belogorlova

doi:10.1055/s-0030-1259103

LETTER

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

Boris A. Trofimov*, Svetlana F. Malysheva, Lidiya N. Parshina, Nina K. Gusarova, Nataliya A. Belogorlova
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, 1 Favorsky Str., 664033 Irkutsk, Russia
Fax: +7(3952)419346; e-Mail: boris_trofimov@irioch.irk.ru;

Abstract

Alle Artikel dieser Rubrik

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

Volltext

Referenzen

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

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) orheated 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.

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

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.