摘要：

Efficient and versatile synthetic routes to functionalized tetrathia[7]helicenes (7㏕Hs) are described. The key intermediates of these methodologies are 2‐bromo3′‐bibenzo[1,2‐b:4,3‐b′]dithiophenes (1), synthesized through a palladiumヽatalyzed homocoupling reaction between two benzo[1,2‐b:4,3‐b′]dithiophene units followed by a regioselective α‐bromination. Direct palladiumヽatalyzed annulation of bromides 1 with internal alkynes provides a set of 7,8ヾisubstituted 7㏕Hs 2 in moderate to good yields (46 %). Otherwise, 7﹎onosubstituted 7㏕Hs 4 have been prepared through Sonogashira coupling of 1 with terminal alkynes, followed by platinumor indium﹑romoted cycloisomerization of alkynyl intermediates 6. Finally, the versatility of bromides 1 has also been demonstrated by using them for the preparation of benzo (hetero) fused 7㏕H derivatives 7 via Suzuki coupling with (hetero)arylboronic acids and the photocyclization of the obtained intermediates 9. Highly versatile procedures have been developed for the synthesis of functionalized tetrathia[7]helicenes, including benzo fused systems, through transition metal﹑romoted annulation reactions of bis(benzodithiophene) species, obtained from 2‐bromo3′‐bibenzo[1,2‐b:4,3‐b′]dithiophene as key intermediate.

展开