An Air-Stable, Reusable, Bimetallic Version of Grubbs’ Catalyst for Alkene Metathesis

Abstract

RCM, cross-metathesis and ring-opening cross-metathesis are efficiently catalyzed by a new, air-stable, bimetallic analog of Grubbs’ Ru-based metathesis catalyst, which can be recovered and recycled.

Key words

metathesis - ruthenium - carbene complexes - catalysis - organometallic reagents

References

• 2a Trnka TM. Grubbs RH. Acc. Chem. Res.  2001,  34:  18 
• 2b Fürstner A. Angew. Chem. Int. Ed.  2000,  39:  3012 
• 2c Grubbs RH. Chang S. Tetrahedron  1998,  54:  4413 
• 2d Schuster M. Blechert S. Angew. Chem. Int. Ed. Engl.  1997,  36:  2036 
• 2e Armstrong SK. J. Chem. Soc., Perkin Trans. 1  1998,  371 
• 2f Grubbs RH. Miller SJ. Fu GC. Acc. Chem. Res.  1995,  28:  446 
• 3a Sanford MS. Love JA. Grubbs RH. J. Am. Chem. Soc.  2001,  123:  6543 
• 3b Dias EL. Nguyen ST. Grubbs RH. J. Am. Chem. Soc.  1997,  119:  3887 
• Recycling catalyst:
• 4a Kingsbury JS. Harrity JPA. Bonitatebus PJ. Hoveyda AH. J. Am. Chem. Soc.  1999,  121:  791 
• 4b Dowden J. Savovic J. Chem. Commun.  2001,  37 
• 4c Fürstner A. Ackermann L. Gabor B. Goddard R. Lehmann CW. Mynott R. Stelzer F. Thiel OR. Chem.-Eur. J.  2001,  7:  3236 
• 4d Ahmed M. Barrett AGM. Braddock DC. Cramp SM. Procopiou PA. Tetrahedron Lett.  1999,  40:  8657 
• 4e For a survey of Ru-based initiators with other alkylidene groups, see: Frenzel U. Nuyken O. J. Polym. Sci. A  2002,  40:  2895 
• We have followed the procedures described in
• 5a Schwab P. Grubbs RH. Ziller JW. J. Am. Chem. Soc.  1996,  118:  100 
• 5b Trnka TM. Day MW. Grubbs RH. Angew. Chem. Int. Ed.  2001,  40:  3441 
• For examples of RCM on organometallic substrates, see:
• 8a Sültemeyer J. Dötz KH. Hupfer H. Nieger M. J. Orgmet. Chem.  2000,  606:  26 
• 8b Zhang L. Herndon JW. Tetrahedron Lett.  2002,  43:  4471 
• 8c Licandro E. Maiorana S. Vandoni B. Perdicchia D. Paravidino P. Baldoli C. Synlett  2001,  757 
• 8d Maity BC. Swamy VM. Sarkar A. Tetrahedron Lett.  2001,  42:  4373 
• 10 Maishal TK. Sinha-Mahapatra DK. Paranjape K. Sarkar A. Tetrahedron Lett.  2002,  43:  2263 

1

Current address: Department of Organic Chemistry, Indian Association for the Cultivation of Science, Kolkata - 700 032, India. E-mail: [e-mail].

6

Vinylferrocene (61 mg, 0.29 mmol) in 1 mL dichloromethane was added to a solution of Ru-benzylidene complex, I, (200 mg, 0.243 mmol) in dichloromethane (5 mL). The reaction mixture was stirred at room temperature for 40 min when color of the solution turned from purple to red-violet. Volume of the solvent was reduced followed by addition of dry methanol at 0 °C, which afforded (Pcy₃)₂Cl₂Ru=C(H)Fc, III, as dark brown solid powder in 87% yield (198 mg). ¹H NMR (CD₂Cl₂): δ 19.00 (s, 1 H, Ru=CH), 4.70 (s, 2 H, Cp), 4.43 (s, 2 H, Cp), 4.14 (s, 5 H, Cp), 2.54 (broad s, 6 H, Pcy₃), 1.21-1.74 (m, 60 H, Pcy₃). ¹³C NMR (CD₂Cl₂): δ 292.14, 104.23, 71.55, 71.21, 69.77, 32.66, 32.04, 30.11, 28.40, 26.98. ³¹P NMR (CD₂Cl₂): δ 34.4 (s, Pcy₃). Details of preparation and complete characterization including crystal structure will be reported separately.

7

Reactions were performed in 1-2 mmol scale in dichloromethane. Yields represent isolated yields of products after purification by chromatography. All compounds were characterized by their IR, ¹H and ¹³C NMR spectra, and satisfactory elemental analyses were obtained for all new compounds.

9

The Ru=CH₂ complex, IV, does not readily react with vinylferrocene at room temperature. However, on heating under reflux in dichloromethane with 1.2-1.5 equivalent of vinylferrocene, complex IV affords >80% yield of complex III.