Synlett 2002(11): 1925-1927
DOI: 10.1055/s-2002-34867
LETTER
© Georg Thieme Verlag Stuttgart · New York

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

Tarun K. Maishal, Amitabha Sarkar*
Division of Organic Chemistry (Synthesis), National Chemical Laboratory, Pune - 411 008, India
Fax: +91(33)4732805; e-Mail: ocas@mahendra.iucs.res.in;
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Publikationsverlauf

Received 13 August 2002
Publikationsdatum:
21. Oktober 2002 (online)

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.

1

Current address: Department of Organic Chemistry, Indian Association for the Cultivation of Science, Kolkata - 700 032, India. E-mail: ocas@mahendra.iacs.res.in.

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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.

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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.

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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.