RuCl₃/PPh₃:  An Efficient Combination for the Preparation of Chiral 1,3-anti-Diols through Catalytic Hydrogenation

Abstract

[reaction: see text] An efficient economical alternative to the commonly used Evans' reagent for the diastereoselective reduction of beta-hydroxy ketones is reported. Thus, ruthenium-mediated hydrogenation of enantioenriched beta-hydroxy ketones using RuCl3 associated to achiral monophosphines allowed the preparation of a series of 1,3-anti-diols in good yields and with a high level of diastereoselectivity. A short screening of ligands pointed out PPh3 as the most effective phosphine, and PCy3 afforded the 1,3-diols with an unexpected moderate syn selectivity.

Synthesis of anti‐1,3‐Diols through RuCl3/PPh3‐Mediated Hydrogenation of β‐Hydroxy Ketones: An Alternative to Organoboron Reagents

“…(2 R ,3 S )‐1‐Benzyloxy‐2‐hydroxy‐3‐methyloctan‐4‐one (27): 6 0.9 g, 77 % yield, colorless oil. R f = 0.25 (cyclohexane/AcOEt, 8:2).…”

“…In this area, borohydride reagents are commonly used, and the development of selective but less expensive and environmentally more benign procedures is desirable. Towards this end, we published recently an operationally simple and waste‐free method for diastereoselective catalytic hydrogenation5 of β‐hydroxy ketones into anti ‐1,3‐diols by using an inexpensive RuCl 3 /phosphane combination 6,7. Herein, we report an expanded substrate scope as well as additional experiments including the study of various ruthenium sources and other transition‐metal complexes.…”

Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs

“…NMR spectra of 8 – 10 exhibited only one set of signals corresponding to the syn -dihydroxy products, indicating an extra high diastereoselectivity ( syn : anti >99:1) during the reduction. To unambiguously determine the diastereomeric ratio, the anti -1,3-diol corresponding to 10 was prepared from 7 by RuCl 3 –PPh 3 -catalyzed hydrogenation [63–64]. However, the two diastereomers had identical proton NMR spectra.…”

Direct conversion of cellulose to sorbitol via an enhanced pretreatment with ionic liquids

“…The low selectivity towards sorbitol makes the reaction uneconomical and this challenge was addressed by the modification of support structures, such as adopting Co‐B, Ni‐P 9 or Ni‐B amorphous alloys and carbon nanotubes (CNT) . In addition to Raney nickel, noble metals such as ruthenium (Ru) (including RuCl 3 ) and platinum (Pt) have been explored as efficient catalysts for glucose hydrogenation which achieved desirable selectivity under relatively low hydrogen pressure conditions . Diverse kinds of support have been employed for those noble metals, for instance, active carbon (AC), HY zeolite and amine functionalized nanoporous polymer .…”