Shvo’s Diruthenium Complex [(η⁵-C₄Ph₄COHOCC₄Ph₄-η⁵)(μ-H)(CO)₄Ru₂]

Biographical Sketches

R. Prabhakaran was born in 1979 and received his Master’s degree in chemistry from Sri Ramakrishna Mission Vidyalaya College of Arts and Science, in Coimbatore, India. He is currently working ­towards his PhD under the supervision of Prof. K. Natarajan at Bharathiar University, Coimbatore, India. His area of interest ­concerns the development of new ruthenium catalysts for efficient organic synthesis.

Introduction

After robust diruthenium complex 1 was reported by ­Shvo, [1] it found enormous utility in organic synthesis as a versatile catalyst, and it is now called Shvo complex. The main reason for its efficient catalytic activity is that it dissociates into 2 and 3 in the reaction mixture under thermal conditions. The 16-electron species 2 and 18-electron complex 3 play vital roles in the catalytic cycle. [2] Recently, a modified procedure for the synthesis of Shvo complex was reported by Bäckvall and co-workers. [3] Shvo complex serves as an effective catalyst in many organic transformations, including the reduction of aldehydes and ketones to alcohols, [4] bimolecular disproportionation reaction of aldehydes to esters, [5] isomerization of allylic alcohols [6] and oxidation of alcohols. [7] In addition, Shvo complex as a racemization catalyst in dynamic kinetic ­resolution (DKR) is well precedented. [8]

Preparation

Shvo complex can be synthesized from Ru(CO)₃(h⁴-Ph₄C₄CO), which is made from Ru₃(CO)₁₂ and tetra­phenylcyclopentadienone. [3]

Abstracts

(A) Shvo complex catalyzed the in situ racemization of secondary alcohols, which then underwent enzyme-catalyzed DKR, in the preparation of enantiomerically pure acetates. [3] The same catalyst has also been used for the racemization of amines and then applied to the synthesis of enantiomerically pure amines. [9]
(B) The combination of enzyme-catalyzed DKR and an aldol reaction provided an access to b-hydroxy ester derivatives with high enantiomeric purity in a one-pot procedure using Shvo complex as catalyst for racemization. [10]
(C) Oxidation of 5-unsaturated 3b-hydroxy steroids to the corresponding 4-en-3-one derivatives can be achieved by acetone at reflux in the presence of a Shvo catalyst. The reaction proceeds via a ruthenium-catalyzed dehydrogenation and subsequent hydrogen transfer to acetone with concomitant double bond migration. [11]
(D) Shvo complex is able to catalyze the transfer dehydrogenation of amines to imines under mild conditions using 2,6-dimethoxybenzoquinone as oxidant. [12]
(E) Complex 1 serves as a catalyst precursor for the hydrogenation of alkynes. [13]
(F) Efficient aerobic oxidation of alcohols was developed via biomimetic catalytic system. Complex 1 dehydrogenates the alcohol and the hydrogens abstracted are transferred to an electron-rich quinone. The hydroquinone thus formed is reoxidized by air with the aid of Co-Salen complex. [2a]

References

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• 2a Csjernvik G. Éll AH. Fadini L. Pugin B. Bäckvall J.-E. J. Org. Chem.  2002,  67:  1657 
• 2b Casey CP. Singer SW. Powell DR. Hayashi RK. Kavana M. J. Am. Chem. Soc.  2001,  123:  1090 
• 3 Persson BA. Larsson ALE. Ray ML. Bäckvall J.-E. J. Am. Chem. Soc.  1999,  121:  1645 
• 4 Menashe N. Salant E. Shvo Y. J. Organomet. Chem.  1996,  514, 97 
• 5 Menashe N. Shvo Y. Organometallics  1991,  10:  3885 
• 6 Bäckvall J.-E. Andreasson U. Tetrahedron Lett.  1993,  34:  5459 
• 7 Jung HM. Choi JH. Lee SO. Kim YH. Park JH. Park J. Organometallics  2002,  21:  5674 
• 8a Pàmies O. Bäckvall J.-E. Chem. Rev.  2003,  103:  3247 
• 8b Kim M.-J. Ahn Y. Park J. Curr. Opin. Biotechnol.  2002,  13:  578 
• 8c Huerta FF. Minidis ABE. Bäckvall J.-E. Chem. Soc. Rev.  2001,  30:  321 
• 9 Pàmies O. Éll AH. Samec JSM. Hermanns N. Bäckvall J.-E. Tetrahedron Lett.  2002,  43:  4699 
• 10 Huerta FF. Bäckvall J.-E. Org. Lett.  2001,  3:  1209 
• 11 Almeida MLS. Koovsk P. Bäckvall J.-E. J. Org. Chem.  1996,  61:  6587 
• 12 Éll AH. Samec JSM. Brasse C. Bäckvall J.-E. Chem. Commun.  2002,  1144 
• 13 Shvo Y. Goldberg I. Czerkie D. Reshef D. Stein Z. Organometallics  1997,  16:  133