Premium
A New Route to Vitamin E Key‐Intermediates by Olefin Cross‐Metathesis
Author(s) -
Malaisé Grégory,
Bonrath Werner,
Breuninger Manfred,
Netscher Thomas
Publication year - 2006
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200690072
Subject(s) - chemistry , catalysis , olefin fiber , olefin metathesis , metathesis , yield (engineering) , medicinal chemistry , salt metathesis reaction , grubbs' catalyst , organic chemistry , stereochemistry , polymerization , polymer , materials science , metallurgy
Ru‐Catalyzed olefin cross‐metathesis (CM) has been successfully applied to the synthesis of several phytyl derivatives ( 2b, 2d – f, 3b ) with a trisubstituted CC bond, as useful intermediates for an alternative route to α ‐tocopheryl acetate (vitamin E acetate; 1b ) ( Scheme 1 ). Using the second‐generation Grubbs catalyst RuCl 2 (C 21 H 26 N 2 )(CHPh)PCy 3 (Cy = cyclohexyl; 4a ) and Hoveyda–Grubbs catalyst RuCl 2 (C 21 H 26 N 2 ){CH‐C 6 H 4 (O‐ i Pr)‐2} ( 4b ), the reactions were performed with various C ‐allyl ( 5a – f, 7a,b ) and O ‐allyl ( 8a – d ) derivatives of trimethylhydroquinone‐1‐acetate as substrates. 2,6,10,14‐Tetramethylpentadec‐1‐ene ( 6a ) and derivatives 6c – e of phytol ( 6b ) as well as phytal ( 6f ) were employed as olefin partners for the CM reactions ( Schemes 2 and 5 ). The vitamin E precursors could be prepared in up to 83% isolated yield as ( E / Z )‐mixtures.