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New Asymmetric Catalysis by (Salen)cobalt(III) Complexes (Salen=[Bis(salicylidene)ethylenediaminato]={{2,2′‐[ethane‐1,2‐diyl]bis[(nitrilo‐ κN )methylidyne]bis[phenolato‐ κO ]}(2−)}) of cis ‐ β ‐Structure: Enantioselective Baeyer‐Villiger Oxidation of Prochiral Cyclobutanones
Author(s) -
Uchida Tatsuya,
Katsuki Tsutomu,
Ito Katsuji,
Akashi Suemi,
Ishii Ayako,
Kuroda Tomomi
Publication year - 2002
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 - 10.1002/1522-2675(200210)85:10<3078::aid-hlca3078>3.0.co;2-1
Subject(s) - chemistry , enantioselective synthesis , cobalt , cationic polymerization , catalysis , medicinal chemistry , metal salen complexes , stereochemistry , polymer chemistry , organic chemistry
A series of chiral (salen)cobalt(III) complexes (salen=[bis(salicylidene)ethylenediaminato]={{2,2′‐[(ethane‐1,2‐diyl)bis[(nitrilo‐ κN )methylidyne]bis[phenolato‐ κO ]}(2−)}) of cis ‐ β structure were prepared and used for the enantioselective Baeyer‐Villiger oxidation of prochiral cyclobutanones with hydrogen peroxide as terminal oxidant. Both cationic (salen)cobalt(III) and neutral iodo(salen)cobalt(III) complexes 3 – 5 and 7 – 12 , respectively, all having a chiral binaphthalenediamine unit, were found to be effective catalysts for the enantioselective Baeyer‐Villiger oxidation ( Tables 1, 3 , and 4 ). In particular, complex 8 bearing electron‐withdrawing F‐atoms showed a good level of enantioselectivity (75–79% ee) in the reactions of 3‐arylcyclobutanones ( Scheme 4 ). On the other hand, complex 12 bearing t Bu groups at C(3) and C(3′) and electron‐withdrawing NO 2 groups at C(5) and C(5′) (trivial numbering) exhibited a high enantioselectivity of 98% ee in the reaction of a tricyclic cyclobutanone ( Table 4 ).