A Polymer-supported Iridium Catalyst for the Stereoselective Isomerisation of Double Bonds

Abstract

A polymer-supported iridium catalyst has been prepared and used in the isomerisation of the double bonds in aryl allylic derivatives with excellent trans selectivity and without the need for conventional work-up procedures.

Key words

iridium - isomerisation - polymer-supported reagents

References

• 1 Ley SV. Baxendale IR. Bream RN. Jackson PS. Leach AG. Longbottom DA. Nesi M. Scott JS. Storer I. Taylor SJ. J. Chem. Soc., Perkin Trans. 1  2000,  3815 
• 2 Baxendale IR. Lee A.-L. Ley SV. Synlett  2001,  1482 
• 3a Yamamoto R. Fujikawa N. Miyanra N. Synth. Commun.  2000,  30:  2383 
• 3b Baudry D. Ephritikhine M. Felkin H. J. Chem. Soc., Chem. Commun.  1978,  694 
• 3c Crabtree RH. Felkin H. Morris GE. J. Chem. Soc., Chem. Commun.  1976,  716 
• Proposed structure of the active species 1 and 2 is based on the solution-phase analogue:
• 5a Haines LM. Singleton E. J. Chem. Soc., Dalton Trans.  1972,  1891 
• 5b

  See ref. 3a.

• 7a Kloosterman JH. Van Boom JH. Chatelard P. Boullanger P. Descotes G. Tetrahedron Lett.  1985,  5045 
• 7b Oltroovt JJ. van Boeckel CAA. de Koning JH. Van Boom JH. Synthesis  1981,  305 

4

Triphenylphosphine on polymer-support had a loading of 3 mmol/g and was purchased from Fluka.

6

General Experimental Procedure: A suspension of the polymer 1 (150 mg) in THF (2.5 mL) was activated by bubbling hydrogen through the suspension until the red polymer turned chrome yellow. The reaction flask was then evacuated and filled with argon before a solution of the aryl allylic derivative (0.25 mmol) in THF (2.5 mL) was cannulated into it. The resulting suspension was agitated at room temperature for 2 h to 15 h. The polymer was removed by filtration and washed with CH₂Cl₂ and THF. The filtrate was concentrated in vacuo and filtered through a plug of silica to yield the isomerised product.

8

All reactions were stopped after 1.5 h and the reaction mixture analysed directly.

9

In a similar manner dillapiole (Table, entry 6) proceeded from quantitative to 91% to 70% (1.5 h reaction runs). The reaction die however proceed to completion when extended reaction times were used (15 h).