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A Versatile Ru Catalyst for the Asymmetric Transfer Hydrogenation of Both Aromatic and Aliphatic Sulfinylimines
Author(s) -
Pablo Óscar,
Guijarro David,
Kovács Gábor,
Lledós Agustí,
Ujaque Gregori,
Yus Miguel
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201102426
Subject(s) - steric effects , transfer hydrogenation , catalysis , chemistry , ligand (biochemistry) , alcohol , substrate (aquarium) , isopropyl alcohol , combinatorial chemistry , isopropyl , chiral ligand , medicinal chemistry , organic chemistry , enantioselective synthesis , ruthenium , biochemistry , oceanography , receptor , geology
Abstract A highly efficient Ru catalyst based on an achiral, very simple, and inexpensive amino alcohol ligand (2‐amino‐2‐methylpropan‐1‐ol) has been developed for the asymmetric transfer hydrogenation (ATH) of chiral N ‐( tert ‐butylsulfinyl)imines. This complex is able to catalyze the ATH of both aromatic and the most challenging aliphatic sulfinylimines by using isopropyl alcohol as the hydrogen source. The diastereoselective reduction of aromatic, heteroaromatic, and aliphatic sulfinylketimines, including sterically congested cases, over short reaction times (1–4 h), followed by desulfinylation of the nitrogen atom, affords the corresponding highly enantiomerically enriched ( ee up to >99 %) α‐branched primary amines in excellent yields. The same ligand was equally effective for the synthesis of both ( R )‐ and ( S )‐amines by using the appropriate absolute configuration in the iminic substrate. DFT mechanistic studies show that the hydrogen‐transfer process is stepwise. Moreover, the origin of the diastereoselectivity has been rationalized.