AUTHOR=Lee Seokwoo , Shin Jae Eui , Yoon Ran , Yoo Hanbin , Kim Sanghee 

TITLE=Annulation of O-silyl N,O-ketene acetals with alkynes for the synthesis of dihydropyridinones and its application in concise total synthesis of phenanthroindolizidine alkaloids

JOURNAL=Frontiers in Chemistry

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2023.1267422

DOI=10.3389/fchem.2023.1267422

ISSN=2296-2646

ABSTRACT=<p>The formation of <italic>N</italic>-heterocycles with multiple substituents is important in organic synthesis. Herein, we report a novel method for the construction of functionalized dihydropyridinone rings through the annulation of an amide <italic>α</italic>-carbon with a tethered alkyne moiety. The reaction of the amide with the alkyne was achieved via <italic>O</italic>-silyl <italic>N</italic>,<italic>O</italic>-ketene acetal formation and silver-mediated addition. Furthermore, the developed method was applied for the total synthesis of phenanthroindolizidine and phenanthroquinolizidine alkaloids. By varying the coupling partners, a concise and collective total synthesis of these alkaloids was achieved.</p>