Electroreduction of Triphenylphosphine Oxide to Triphenylphosphine in the Presence of Chlorotrimethylsilane

Abstract

Electroreduction of triphenylphosphine oxide to triphenylphosphine in an acetonitrile solution of tetrabutylammonium bromide in the presence of chlorotrimethylsilane was performed successfully in an undivided cell fitted with a zinc anode and a platinum cathode under constant current. A plausible mechanism involving, (1) one-electron reduction of triphenylphosphine oxide generating the corresponding anion radical [Ph₃P^˙ -O^-], (2) subsequent reaction with chlorotrimethylsilane affording the (trimethylsiloxy)triphenylphosphorus radical [Ph₃P^˙ -OSiMe₃], and (3) further one-electron reduction followed by P-O bond fission leading to triphenylphosphine is proposed. In a similar manner, electroreduction of some triarylphosphine oxides and alkyldiarylphosphine oxides was executed to give the corresponding phosphine derivatives in good to moderate yields.

Key words

reduction - electron transfer - phosphorus - silicon

References

• 1a Maercker A. In Organic Reactions   Vol. 14:  John Wiley & Sons; New York: 1965.  Chap. 3.
• 1b Boutagy J. Thomas R. Chem. Rev.  1974,  74:  87 
• 2a Hughes DL. In Organic Reactions   Vol. 42:  John Wiley & Sons; New York: 1992.  Chap. 2.
• 2b Mitsunobu O. Yamada M. Bull. Chem. Soc. Jpn.  1967,  40:  2380 
• 2c Mukaiyama T. Matsueda R. Maruyama H. Bull. Chem. Soc. Jpn.  1970,  43:  1271 
• 3a Mukaiyama T. Araki M. Takei H. J. Am. Chem. Soc.  1973,  95:  4763 
• 3b Corey EJ. Nicolaou KC. J. Am. Chem. Soc.  1974,  96:  5614 
• 3c Corey EJ. Nicolaou KC. Melvin LS. J. Am. Chem. Soc.  1975,  97:  653 
• 3d Modification: Gerlach H. Thalmann A. Helv. Chim. Acta  1974,  57:  2661 
• 4a Appel R. Angew. Chem., Int. Ed. Engl.  1975,  14:  801 
• 4b Calzada JG. Hooz J. Org. Synth.  1974,  54:  63 
• 5a Staudinger H. Meyer J. Helv. Chim. Acta  1919,  2:  635 
• 5b Gololobov YG. Zhmurova IN. Kasukhin LF. Tetrahedron  1981,  37:  437 
• 5c Scriven EFV. Turnbull K. Chem. Rev.  1988,  88:  297 
• 5d Gololobov YG. Kasukhin LF. Tetrahedron  1992,  48:  1353 
• 5e Shah S. Protasiewicz JD. Coord. Chem. Rev.  2000,  210:  181 
• 6 Phosphorus is obtained economically from limited regions of the world: Kuroda A. Takiguchi N. Kato J. Ohtake H. J. Environ. Biotech.  2005,  4:  87 
• 7 As an another approach, catalytic Wittig reaction using 3-methyl-1-phenylphospholane 1-oxide was reported: O’Brien CJ. Tellez JL. Nixon ZS. Kang LJ. Carter AL. Kunkel SR. Przeworski KC. Chass GA. Angew. Chem. Int. Ed.  2009,  48:  6836 
• 8a Fritzsche H. Chem. Ber.  1965,  98:  171 
• 8b Coumbe T. Lawrence NJ. Muhammad F. Tetrahedron Lett.  1994,  35:  625 
• 8c Marsi FM. J. Org. Chem.  1974,  39:  265 
• 9a Horner L. Hoffmann H. Beck P. Chem. Ber.  1958,  91:  1583 
• 9b Imamoto T. Tanaka T. Kusumoto T. Chem. Lett.  1985,  14:  1491 
• 9c Griffin S. Heath L. Wyatt P. Tetrahedron Lett.  1998,  39:  4405 
• 9d Nelson GE. inventors; US  4,507,502.  ; Chem. Abstr. 1985, 103, 37617
• 9e Busacca CA. Raju R. Grinberg N. Haddad N. James-Jones P. Lee H. Lorenz JC. Saha A. Senanayake CH. J. Org. Chem.  2008,  73:  1524 
• 9f Malpass DB, and Yeargin GS. inventors; US  4,113,783.  ; Chem. Abstr. 1979, 90, 23256
• 10 Handa Y. Inanaga J. Yamaguchi M. J. Chem. Soc., Chem. Commun.  1989,  298 
• 11 Mathey F. Maillet R. Tetrahedron Lett.  1980,  21:  2525 
• 12 Dockner T. Angew. Chem.  1988,  100:  699 
• 13 Timokhin BV. Kazantseva MV. Blazhev DG. Rokhin AV. Russ. J. Gen. Chem.  2000,  70:  1310 ; Chem. Abstr. 2001, 134, 311265
• 14a Iorga B. Camichael D. Savignac P. C. R. Acad. Sci., Ser. IIC  2000,  3:  821 
• 14b Hermeling D, Hugo R, Lechtken P, Rotermund GW, and Siegel H. inventors; DE  19,532,310.  ; Chem. Abstr. 1997, 126, 199670
• 14c Masaki M. Fukui K. Chem. Lett.  1977,  6:  151 
• Triphenylphosphorus dichloride (3a) is also prepared by treatment of 2 with chlorinating reagents such as diphosgene, triphosgene, and phosphorus pentachloride.
• 15a Rao VJ, and Reddy AM. inventors; IN  1996-DE1812.  ; Chem. Abstr. 2007, 146, 402090
• 15b Li H, Chen Z, Wu L, Wang C, and Hu B. inventors; CN  1,660,862.  ; Chem. Abstr. 2006, 144, 488805
• 15c Horner L. Hoffmann H. Beck P. Chem. Ber.  1958,  91:  1583 
• 16 Theoretical calculation: Mo O. Eckert-Maksic YM. Maksic ZB. Alkorta I. Elguero J. J. Phys. Chem. A.  2005,  109:  4359 
• 17 Masaki M, and Kaketani N. inventors; JP  53-034,725.  ; Chem. Abstr. 1978, 89, 109953
• 18 Fukui K, Kaketani N, Kita J, and Fujimura S. inventors; JP  55-149,293.  ; Chem. Abstr. 1981, 94, 175259
• 19 Horner L. Beck P. Hoffmann H. Chem. Ber.  1959,  92:  2088 
• 20 Hermeling D, Siegel H, Hugo R, and Rotermund GW. inventors; EP  725,073.  ; Chem. Abstr. 1996, 125, 195993
• 21 Wettling T. inventors; EP  5,48,682.  ; Chem. Abstr. 1993, 119, 139547
• 22 Young DA, and Brannock KC. inventors; US  3,780,111.  ; Chem. Abstr. 1974, 80, 60039
• 23a Organic Electrochemistry   4th ed.:  Lund H. Hammerich O. Marcel Dekker; New York: 1991. 
• 23b Torii S. In Electroorganic Reduction Synthesis   Kodansha & Wiley-VCH; Tokyo/Weinheim: 2006. 
• 23c New Developments in Organic Electrosynthesis   Fuchigami T. CMC; Tokyo: 2004. 
• 23d Electroorganic Chemistry, Kagaku Zokan   Vol. 86:  Osa T. Shono T. Honda K. Kagaku Dojin; Kyoto: 1980. 
• 24a Santhanam KSV. Bard AJ. J. Am. Chem. Soc.  1968,  90:  1118 
• 24b Raju T, Kulangiappar K, Kulandainathan MA, Muthukumaran A, and Krishnan V. inventors; IN  2002-DE793.  ; Chem. Abstr. 2007, 147, 235305
• 25 CRC Handbook of Chemistry & Physics   74th ed.:  Lide DR. CRC Press; London: 1993. 
• 27 Yano T. Hoshino M. Kuroboshi M. Tanaka H. Synlett  2010,  801 
• 28 Yano T. Kuroboshi M. Tanaka H. Tetrahedron Lett.  2010,  51:  698 
• 29 Kuroboshi M. Yano T. Kamenoue S. Kawakubo H. Tanaka H. Tetrahedron  2011,  67:  5825 
• 30 Tanaka H. Yano T. Kobayashi K. Kamenoue S. Kuroboshi M. Kawakubo H. Synlett  2011,  582 

26

Since 3a is highly moisture sensitive, 3a was used without purification.

31

Among thus far examined solvents, MeCN was the only solvent effective for the present purpose; thus, electro-reduction of 2a to 1a hardly occurred in THF, DMSO, DMF, and 1,4-dioxane. The electroreduction proceeded in a mixture of THF and MeCN (4:1 to 1:4).

32

As a supporting electrolyte, Bu₄NOTf, Bu₄NBF₄, and Bu₄NClO₄ could be used to give 1a in slightly lower yields (42, 38, and 52%, respectively). The electroreduction of 2a proceeded without supporting electrolyte to give 1a in 41% yield.

33

One singlet signal appeared at δ = 32.5 ppm in the ^³¹P NMR of a mixture of 2a, Me₃SiCl, and Bu₄NBr. On the other hand, a mixture of 2a and Me₃SiBr showed a singlet peak at δ = 48.7 ppm. These results suggest that Me₃SiCl would react partially with Bu₄NBr to give Me₃SiBr, which would inter-act with 1a to form a trace amount of [Ph₃P⁺-O-SiMe₃]Br^-. However, since the electroreduction of Ph₃P=O (2a) proceeded without Br^- source (ref. 32), the electroreduction of 2a seems to proceed mainly through the ECEC mechanism (Scheme  [6] ).