Bis(tetrahydrofuran)(5,10,15,20-tetramesitylporphyrinato)ruthenium(II) [Ru11TMP(THF)2] and the corresponding p-tolylporphyrin [Ru11TTP(THF)2] have been found to catalyze the cis-trans isomerization of epoxides under mild conditions. For 0-methylstyrene oxide an equilibrium ratio of 5.4:1 (trans/cis) was achieved with either isomer indicating a free energy difference of 1 kcal/mol. Inhibition of the isomerization by added olefins was observed and attributed to olefin coordination to ruthenium(II). cis-β-Methylstyrene oxide readily formed an adduct with Ru11TMP(CO), while the trans isomer did not. The isomerization of trans-(1S,2S)-β-methylstyrene oxide gave only cis-(1 R,2S)-β-methylstyrene oxide. A mechanism for epoxide isomerization involving homolytic cleavage of the C1-O bond to give carbon radical intermediate is proposed.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry