Thermal Synthesis of 3‐Bromothieno[3,2‐c]pyridin‐4‐(5H)‐one: A Telescoped Procedure with Tributylamine

Abstract

3‐Bromothieno[3,2‐c]pyridine‐4‐(5H)‐one (1) was prepared from (2E)‐3‐(4‐bromo‐2‐thienyl)‐2‐propenoic acid (3) by the Eloy–Deryckere thermal benzo/heteropyridinone synthesis. A telescoped procedure was developed, which reduces some of the risk associated with the classic procedure. Use of tributylamine as an additive in this process was shown to facilitate E/Z‐isomerization of the intermediate vinyl isocyanate and lower the temperature necessary for the overall thermal process.

2H-Azirine-2-carbonyl Azides: Preparation and Use as N-Heterocyclic Building Blocks

“…[6π]-Electrocyclization involving the NC bond of the isocyanates, generated via the Curtius rearrangement, with the formation of fused pyridin-2­(1 H )-ones derivatives, occurs normally at high temperatures: 240 °C in diphenyl ether, 180 °C in o -dichlorobenzene ( o -DCB), 170 °C in p -cymene, 180 °C in o -DCB in the presence of Hg­(OAc) 2 as a catalyst, and 170 °C in o -DCB in the presence of I 2 as a catalyst . The mentioned electrophilic cyclization is the characteristic of electron-rich azoles (Scheme ).…”

“…The mentioned electrophilic cyclization is the characteristic of electron-rich azoles (Scheme ). − , When a substituted phenyl ring is involved in the cyclization, a donor substituent accelerates the reaction…”

Cutting edge of diphenyl phosphorazidate (DPPA) as a synthetic reagent – A fifty-year odyssey

“…33 A telescoped procedure was developed in the conversion of the thiophene carboxylic acid 49 to the lactam 53 . 34 Reaction of 49 with DPPA-tributylamine gave the acyl azide 50 , which was rearranged to the isocyanate ( E )- 51 . Addition of tributylamine facilitated E / Z isomerization to give ( Z )- 51 .…”