Catalytic isomerization of branched allylic alcohols by water-soluble [RuCp(OH2)(PTA)2](CF3SO3) and [RuCp(OH2)(mPTA)2](CF3SO3)3

Abstract

The isomerization of substituted allylic alcohols, including α-vinyl benzyl alcohol, trans-1,3-diphenyl-2-propen-1-ol, cinnamyl alcohol, coniferyl alcohol, 4-nitrocinnamyl alcohol, farnesol, 1,5-hexadien-3,4-diol, (1R)-(−)-myrtenol and S,R-(−)-carveol, catalyzed by the [RuCp(OH₂)(PTA)₂](CF₃SO₃) (1) and [RuCp(OH₂)(mPTA)₂](CF₃SO₃)₃ (2) (PTA = 1,3,5-triaza-7-phosphaadamantane, mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane) complexes was examined in pure water and water-containing media. The isomerization of the chalcone trans-1,3-diphenyl-2-propen-1-ol catalyzed by 1 to produce the natural product propiophenone displays the highest known turnover number for this reaction to date (TON = 200 and TOF_5h = 40 h⁻¹). A study delving into the catalytic reaction mechanisms was carried out, aiming to understand the influence of different functional groups on the studied isomerization processes. The intermediates of the isomerization of α-vinylbenzyl alcohol and 1,5-hexadien-3,4-diol catalyzed by 1 and 2 were isolated and characterized by NMR spectroscopy.