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2005
Fused pyridine derivatives
R 0450
One-Pot Synthesis of Helical Aromatics: Stereoselectivity, Stability Against Raceand Assignment of Absolute Configuration Assisted by Experimental
12- 155 mization,
and Theoretical Circular Dichroism. — Under solvent-free conditions and either
conventional heating (∆) or microwave irradiation (MW), the condensation of diamine
(I) with mono- or dicarboxylic acids (II) and (IV) in the presence of a Lewis acid affords
the desired dibenzophenanthrolines. MW drastically shorts the reaction times. Some of
these derivatives are resolved into their respective helical (P)- and (M)-enantiomers.
By use of optically pure acid (S)-(IVc) under MW, the product is obtained with 100%
diastereo- and 50% enantioselectivity. Under ∆ a racemic mixture is formed. Since the
product (Vc) shows a pronounced stability towards racemization even at elevated temperatures, racemization in the starting acid or in a reaction intermediate seems to take
place under ∆. — (WATANABE, M.; SUZUKI, H.; TANAKA*, Y.; ISHIDA, T.;
OSHIKAWA, T.; TORI-I, A.; J. Org. Chem. 69 (2004) 23, 7794-7801; Dep. Mater.
Sci., Fac. Eng., Shizuoka Univ., Hamamatsu, Shizuoka 432, Japan; Eng.) — Klein
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