Synthesis of Annulated Thiophenes Involving Benzo‐DMTHFs/Triflic acid‐Mediated Domino Reactions

Abstract

A facile protocol for synthesis of naphth-annulated thiophenes has been developed via benzo-DMTHFs/triflic acid-mediated annulation of thiophenes. Furthermore, this methodology was found to be successful with substituted benzo-DMTHFs as well as higher homologues of benzo-DMTHF. tetraacetate, [16] ZnBr 2 /SiO 2 catalyzed annulation of electron-rich arenes with acetyl bromide-phthalaldehydes, [17a] Lewis acidinduced cyclization of aldehydes, [17b] A Lewis acid-mediated annulation of 2/3-(bromomethyl)indoles with arenes/heteroarenes, [18] palladium-catalyzed annulation of an in situ generated aryne annulation by o-halostyrene, [19] HI/P-mediated reductive [a] Dr.Figure 1. Synthesis of naphth-annulated arenes and heteroarenes.

Efficient Synthesis and Functionalization of 3-Bromonaphtho[2,3-b]thiophene

“…Mohanakrishnan subsequently showed HI/red phosphorus could effect both the reduction and cyclization step. 9 Further studies by Mohanakrishnan and co-workers also showed that malonylidene units could be used as an aldehyde surrogate in comparable chemistry with very electron-rich arenes, leading to elimination of a malonate rather than water. 10 In another approach, Steinmetz­ and co-workers accessed 3-bromonaphthothiophene ( 2d ) via a more successful modification of the Carruthers­ method (Scheme 1 , equation 4).…”