Dithieno pyridines

Treatment of the thiophene congener of Troger s base 15a with HC1 in refluxing MeOH furnished the dithieno-pyridine 73. Although the mechanism of such a rearrangement was not clarified, the intervention of a quinone-imine-methide intermediate was suggested (Equation 3) <2002J(P1)1963>. 

Synthesis of dithieno[2,3-A2,3-,7]thiophene derivatives 122 has been accomplished through the Heck reaction of 3-(4-bromo-2-thienyl)acrylic acid 302 to afford 3-(2,4-thienylene)diacrylic acid 303 which was cyclized with thionyl chloride and a catalytic amount of pyridine to the dichloride 120 in 75% yield (Scheme 56) <2005MOL279>. 

Nitration of dithieno[3,2-b 3, 2 -thiophene ring to form a mixture of isomers 185 and 186 in a ratio of 40 60 (1993JHC561). For dithieno[3,2-6 3, 4 -<7]pyridine (187), the replacement occurs predominantly at the 3,4-annulated ring. The 2-nitro- and 8-nitro isomers 188 and 189, respectively, were obtained in a ratio of 33 67. 

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