- Practical Synthesis of Optically Pure Bifunctionalized Heterohelicenes
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Optically active 2-(hydroxymethyl)- and 2-(ethylthiocarbonyl)[1]benzothieno[5′,4′ :2.3][1]benzothieno [4′.5 :4,5]-thieno[3,2-f]quinolines containing π-excessive thiophene and π-deficient pyridine units were prepared by the use of exo-3-amino-2-hydroxybornane as a chiral auxiliary. This procedure consists of separation of the helical diastereomers prepared by photocyclization of 1,2-diarylethylenes and removal of the chiral auxiliary by a thiolate ion. Large scale preparation of the helicenes can be accomplished by a modified procedure of the photocyclization reaction. Optical purities of both enantiomers of 2-(hydroxymethyl)- and 2-(ethylthiocarbonyl)[1] benzothieno[5′ ,4′ : 2,3][I]benzothieno[4′.5′ : 4,5]-thieno[3,2-f lquinolines were >99.5%. Their absolute configurations were determined by comparison of CD spectra.
- Osuga, Hideji,Suzuki, Hitomi,Tanaka, Kazuhiko
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p. 891 - 897
(2007/10/03)
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- Synthesis and crystal structure of chiral bifunctional helicenes with π-deficient pyridine and π-excessive thiopene units
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Both enantiomers of new bifunctional helicenes constructed from π-excessive 2-(hydroxymethyl)thiophene and π-deficient pyridine rings have been prepared using (1R, 2S, 3R, 4S)-3-amino-2-hydroxybornane as a chiral auxiliary. The X-ray crystal structure reveals the intermolecular hydrogen bond between the hydroxy group of the helicene and the pyridine nitrogen atom of the adjacent molecule. The non-bonded distance between the nitrogen atom and the oxygen atom is 2.72 A, and the interplanar angle between the terminal rings is 45.3°.
- Tanaka, Kazuhiko,Kitahara, Yoshinori,Suzuki, Hitomi,Osuga, Hideji,Kawai, Yasushi
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p. 5925 - 5928
(2007/10/03)
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