Premium
Definitive structural assignment of condensation products from anthranilamide and 3‐amino‐2‐carbamoylthiophene with ketones. Formation of tetrahydroquinazolinones and their thiophene isosteres
Author(s) -
Klemm Leroy H.,
Weakley Timothy J. R.,
Gilbertson Robert D.,
Song YangHeon
Publication year - 1998
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570350605
Subject(s) - chemistry , thiophene , condensation , organic chemistry , stereochemistry , combinatorial chemistry , thermodynamics , physics
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.