Definitive structural assignment of condensation products from anthranilamide and 3-amino-2-carbamoylthiophene with ketones. Formation of tetrahydroquinazolinones and their thiophene isosteres

✍ Scribed by Leroy H. Klemm; Timothy J. R. Weakley; Robert D. Gilbertson; Yang-Heon Song

• Publisher: Journal of Heterocyclic Chemistry
• Year: 1998
• Tongue: English
• Weight: 367 KB
• Volume: 35
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570350605

✦ Synopsis

Abstract

Products formed from dehydrative cyclization of cyclopentanone, cyclohexanone, and cycloheptanone with anthranilamide (2) under neutral or acidic conditions are established as the spiro compounds 2,2‐polymethylene‐1,2,3,4‐tetrahydroquinazolin‐4‐ones 6 by means of (a) the presence of a ^13^C nmr signal at 66–79 ppm for atom C‐2 and (b) X‐ray crystallography on the tetramethylene compound 6a. Analogously, products from reactions of these cycloalkanones with 3‐amino‐2‐carbamoylthiophene are now shown by ^13^C nmr spectra to have structures isosteric to 6, i.e. 5,5‐polymethylene‐4,5,6,7‐tetrahydrothieno[2,3‐e]pyrimidin‐7‐ones 5, rather than the chelate ring structures previously proposed. Additionally, conflicting literature reports on product 3 from reaction of acetone with 2 are partially clarified. Correlation of ^13^C chemical shifts in systems 3, 5, and 6 is presented.