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Practical Asymmetric Catalytic Synthesis of Spiroketals and Chiral Diphosphine Ligands
Author(s) -
Wang Xubin,
Guo Peihua,
Wang Xiaoming,
Wang Zheng,
Ding Kuiling
Publication year - 2013
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201300380
Subject(s) - chemistry , catalysis , difluoride , asymmetric carbon , asymmetric hydrogenation , enantioselective synthesis , palladium , organic chemistry , combinatorial chemistry , medicinal chemistry , optically active
Abstract A practical procedure has been developed for efficient synthesis of chiral aromatic spiroketals and the relevant diphosphine ligands. The procedure includes first asymmetric hydrogenation of readily available α,α′‐bis(2‐benzyloxyarylidene) ketones catalyzed by the Ir(I)/SpinPHOX ( S , S )‐ 1a (0.5–1 mol%) and subsequent hydrogenative deprotection of the resultant benzyl ethers catalyzed by palladium on carbon (Pd/C), as well as simultaneous spiroketalization of the corresponding diphenolic ketones by ( S , S )‐ 1a in one pot. The corresponding chiral aromatic spiroketals ( R , R , R )‐ 4a–j have been obtained in high yields (77–94%) with good diastereoselectivities ( trans / cis =81/19 to 96/4), and excellent enantioselectivities for the trans products (97–>99% ee ). In addition, the reaction of aromatic spiroketal difluoride ( R,R,R )‐ 4b with potassiodiarylphosphide (KPAr 2 ) in refluxing tertahydrofuran (THF) has also provided an alternative and practical synthesis of chiral spiroketal‐based diphosphine (SKP) ligands in 78–95% yields on multigram scale.