Rare Medium-Sized Rings Prepared via Hydrolytic Imidazoline Ring Expansion (HIRE)

The hydrolytic imidazoline ring expansion
(HIRE) methodology was
extended to readily available tetracyclic [1,4]­thiazepines as well
as sulfoxide and sulfone analogs thereof. The reactions resulted in
the facile formation of a rare medium-sized [1,4,7]­thiazecine ring
system that has an emerging utility in bioactive compound design.
Comparing the HIRE rates for representative compounds in the three
groups of substrates allowed drawing some generalizations about the
substituent effects on the course of the reaction.