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Olefin Epoxidation Catalyzed by cis ‐Dioxdomolybdenum(VI) Complexes Containing Chiral Alkoxo‐Imino Ligands Derived from (+)‐α‐Pinene
Author(s) -
Chahboun Ghaita,
Brito Jose Angel,
Royo Beatriz,
El Amrani Mohamed Amin,
GómezBengoa Enrique,
Mosquera Marta E. G.,
Cuenca Tomás,
Royo Eva
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201200144
Subject(s) - chemistry , catalysis , olefin fiber , chemoselectivity , cyclooctene , stereoselectivity , molybdenum , medicinal chemistry , enantioselective synthesis , alcohol , stereochemistry , organic chemistry
New chiral cis ‐dioxidomolybdenum compounds [MoO 2 (acac)( R N,O)] [R = Bn ( 1 ), pic ( 2 )] and [{MoO 2 (acac)} 2 {μ‐(O,N,N,O)}] ( 3 ) have been synthesized by treating [MoO 2 (acac) 2 ] withthe corresponding enantiomerically pure alcohol‐iminocompounds derived from (+)‐α‐pinene modification, ( R N,OH) (R = Bn, pic) and (HO,N,N,OH), respectively. Compound [MoO 2 Cl 2 (O,N,N,O)] ( 4 ) has also been prepared. All the compounds were fully characterized both in solution and in the solid state, including by single‐crystal X‐ray diffraction analysis of enantiomerically pure 3 . DFT studies support the stereoselectivity of the synthesis of compound 3 . Catalytic olefin epoxidation studies were performed with cis ‐cyclooctene, ( R )‐limonene, and trans ‐β‐methylstyrene by using derivatives 1 – 4 as catalyst precursors and tert ‐butyl hydroperoxide (TBHP) or H 2 O 2 as oxidant. All the catalytic systems showed high chemoselectivity irrespective of the terminal oxidant used. The molybdenum compounds exhibited medium to high catalytic activity at mild reaction temperatures, but no substantial optical induction was observed. This study represents the first use of chiral monoacetylacetonato‐ cis ‐dioxidomolybdenum compounds as homogeneous olefin epoxidation catalysts.