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Communication | Regular issue | Vol 57, No. 12, 2002, pp.2227-2230
Published online, 1st January, 1970
DOI: 10.3987/COM-02-9612
Synthesis of New Thiopyrylocyanines Incorporated Thiopyrano[2,3-b]indole Ring as the Main Constituent

Yoshinori Tominaga,* Yasuhiro Shigemitsu, and Shun-ichi Hirayama

*Nagasaki University, Center of Instrumental Analysis, 1-14, Bunkyo-machi, Nagasaki 852-8521, Japan

Abstract

The Diels-Alder product, dimethyl 5-methyl-4a-methyl-1-methylthiothiopyrano[4,3-b]indole-3,4-dicarboxylate (2b), which was obtained by the reaction of methyl 1,2-dimethylindole-3-dithiocarboxylate (1b) with DMAD (dimethyl acetylenedicarboxylate), was easily converted to a 1,5-dimethyl-2,3-bis(methoxycarbonyl)indolo[2,3-b]thiopyrylium perchlorate (5) as the key intermediate for the thiopyrylocyanine and merocyanine dyes. Compounds (5 and 6) were allowed to react with aromatic aldehydes and some electrophilic reagents to yield cyanine and merocyanine dyes (8a-c, 10-12) in good yields.