Synthesis of Tetrasubstituted Thieno[3,2‐ b ]pyridin‐5(4 H )‐one Derivatives as a Heterocyclic Scaffold for Multisite‐specific Fluorous Fluorescent Tagging and Fluorous Solid‐Phase Extraction

Tetrasubstituted thieno[3,2‐ b ]pyridin‐5(4 H )‐one derivatives were selected as a highly functionalized heterocyclic scaffold for a multisite‐specific tagging process utilizing a previously devised fluorous fluorescent tag system. A suitable synthetic method was established for the 7‐alkoxy‐2,4,6‐trisubstituted‐thieno[3,2‐ b ]pyridin‐5(4 H )‐one derivatives, and incorporating t ‐butoxycarbonyl‐functionalized building blocks into the reaction sequence produced precursors that could be used in the tagging process. Fluorous solid‐phase extraction facilitated the purification of the tagged target compounds after a series of reactions, including t ‐Bu deprotection/ N ‐hydroxysuccinimidyl ester formation/amidation.