Synlett 2013; 24(6): 773-774
DOI: 10.1055/s-0032-1318264
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© Georg Thieme Verlag Stuttgart · New York

(Triphenylphosphoranylidene)ketene: The Bestmann Ylide

Mark Bartlett
School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand   Email: Mark.Bartlett@vuw.ac.nz
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Further Information

Publication History

Publication Date:
07 March 2013 (online)

Introduction

(Triphenylphosphoranylidene)ketene (1), also known as the Bestmann ylide, is a reagent with intriguing properties and proven synthetic utility.[ 1 ] After early reports of this compound by others,[ 2 ] H. J. Bestmann popularized the use of 1 in the formation of a wide range of (triphenyl­phosphoranylidene)acyl derivatives.[ 3 ] The Bestmann ylide (1) is now commercially available and used in a wide range of reactions. Alternatively, 1 can be prepared by the deprotonation of methyl (triphenylphosphoranylidene)acetate (2, Scheme [1)] [ 4 ] A variety of strong bases have been used to perform this transformation,[ 5 ] with NaHMDS being particularly efficient and convenient.

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Scheme 1 Preparation of the Bestmann ylide

Interestingly, the X-ray crystal structure of 1 shows a 145.5° P=C=C bond angle and a remarkably short C=C bond length (1.21 Å).[ 6 ] These properties are derived from the combination of three resonance structures (Scheme [2]), which highlight the two overlapping, orthogonal π-systems that stabilize the molecule. This makes the reactivity of the Bestmann ylide significantly different from typical ketenes and phosphorus ylides. The Bestmann ylide is surprisingly stable and can be stored under inert atmosphere at ambient temperature for months.[ 4 ]

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Scheme 2 Resonance structures of 1
 
  • References

  • 1 Bestmann HJ. Angew. Chem., Int. Ed. Engl. 1977; 16: 349
    • 2a Matthews CN, Birum GH. Tetrahedron Lett. 1966; 7: 5707
    • 2b Birum GH, Matthews CN. J. Am. Chem. Soc. 1968; 90: 3842

      For representative examples, see:
    • 3a Bestmann HJ, Schmid G, Sandmeier D. Tetrahedron Lett. 1980; 21: 2939
    • 3b Bestmann HJ, Schmid G, Sandmeier D. Chem. Ber. 1980; 113: 912
    • 3c Bestmann HJ, Schobert R. Angew. Chem., Int. Ed. Engl. 1985; 24: 790
    • 3d Bestmann HJ, Schobert R. Synthesis 1989; 419
    • 3e Bestmann HJ, Kellermann W. Synthesis 1994; 1257
  • 4 Schobert R. Org. Synth. 2009; 82: 140
    • 5a Bestmann HJ, Schmidt M, Schobert R. Synthesis 1988; 49
    • 5b Buckle J, Harrison PG. J. Organomet. Chem. 1974; 77: C22
  • 6 Daly JJ, Wheatley PJ. J. Chem. Soc. A 1966; 1703
    • 7a Boeckman Jr RK, Pero JE, Boehmler DJ. J. Am. Chem. Soc. 2006; 128: 11032
    • 7b Boeckman Jr RK, Song X, Pero JE. J. Am. Chem. Soc. 2006; 71: 8969
    • 8a Schobert R, Stangl A. Tetrahedron Lett. 2005; 46: 1127
    • 8b Schobert R, Siegfried S, Gordon GJ. J. Chem. Soc. Perkin Trans 1 2001; 2393
  • 9 Pachali S, Hofmann C, Rapp G, Schobert R, Baro A, Frey W, Laschat S. Eur. J. Org. Chem. 2009; 2828
  • 10 Jung ME, Yoo D. Org. Lett. 2011; 13: 2698

    • For additional examples, see:
    • 11a Marcos IS, Benéitez A, Moro RF, Basabe P, Díez D, Urones JG. Tetrahedron 2010; 66: 8605
    • 11b Schobert R, Seibt S, Mahal K, Ahmad A, Biersack B, Effenberger-Neidnicht K, Padhye S, Sarkar FH, Mueller T. J. Med. Chem. 2011; 54: 6177
    • 12a Fedoseyenko D, Raghuraman A, Ko E, Burgess K. Org. Biomol. Chem. 2012; 10: 921
    • 12b Raghuraman A, Eunhwa K, Perez LM, Ioerger TR, Burgess K. J. Am. Chem. Soc. 2011; 133: 12350
  • 13 Schlenk A, Diestel R, Sasse F, Schobert R. Chem.–Eur. J. 2010; 16: 2599
    • 14a Kitson RR. A, Taylor RJ. K, Wood JL. Org. Lett. 2009; 11: 5338
    • 14b Kitson RR. A, McAllister GD, Taylor RJ. K. Tetrahedron Lett. 2011; 52: 561
  • 15 Risi RM, Burke SD. Org. Lett. 2012; 14: 1180
  • 16 Clark TP, Landis CR, Freed SL, Klosin J, Abboud KA. J. Am. Chem. Soc. 2005; 127: 5040