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2005
Benzopyran derivatives
R 0350
Asymmetric Synthesis of 3-Substituted 3,4-Dihydroisocoumarins via StereoselecAddition of Laterally Lithiated Chiral 2-(o-Tolyl)oxazolines to Aldehydes
31- 134 tive
Followed by Diastereomer-Selective Lactonization. — A highly diastereoselective
addition of laterally lithiated oxazoline (I) to aldehydes proceeds in diethyl ether in the
presence of TMEDA, which possesses high coordinating ability. From the resulting
diastereomeric product mixture the major diastereomers (III) lactonize much faster than
the minor diastereomers under acidic conditions. Thus, the target dihydroisocoumarins
(IV) are obtained with up to 97% enantioselectivity. — (KUROSAKI, Y.; FUKUDA,
T.; IWAO*, M.; Tetrahedron 61 (2005) 13, 3289-3303; Dep. Appl. Chem., Fac. Eng.,
Nagasaki Univ., Bunkyo, Nagasaki 852, Japan; Eng.) — Klein
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