POCl₃/Sulfoxide and AcCl/Sulfoxide Mediated Chlorination of Pyrrolo[2,1-a]isoquinolines

Abstract

We have developed an efficient chlorination of pyrrolo[2,1-a]isoquinoline derivatives using POCl 3 as the chlorine source and tetramethylene sulfoxide as a promoter. A series of pyrrolo[2,1-a]isoquinolines, polysubstituted pyrroles, and naphthols have been readily chlorinated under mild reaction conditions (26 examples, up to >99% yield). AcCl can also act as the chlorine source competently in this chlorination reaction.

POCl3/Sulfoxide-Promoted Synthesis of Indolizino[8,7-b]indoles

“…In particular, a large number of elegant sulfoxide based halocyclizations have been reached through oxidative halogenation/cyclization cascade, providing highly functionalized architectures . In our previous reports, we found that dimethyl sulfoxide and tetramethylene sulfoxide could be able to serve as oxidant competently along with simple bromine and chlorine sources, yielding brominated and chlorinated heteroarenes and arenes efficiently. , Inspired by recent achievements on halocyclization and electrophilic dearomatization of indoles, we hypothesized that in situ formed chlorinating agent from sulfoxide and chlorine source may be employed to trigger dearomative cyclization of pyrrole-tethered indoles. Chlorinated indolizinoindoles may be constructed directly under these mild reaction conditions.…”