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Spectral and structural correlations of 1,4‐ and 3,4‐dihydroquinazolines
Author(s) -
Smith James G.,
Sheepy John M.
Publication year - 1975
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.5570120203
Subject(s) - chemistry , substituent , methyl iodide , iodide , alkylation , nucleophile , spectral line , infrared spectroscopy , medicinal chemistry , stereochemistry , organic chemistry , catalysis , physics , astronomy
Alkylation of the nucleophilic addition product of 2,4‐diphenylquinazoline and organometallic derivatives produced a mixture of 1,4‐ and 3,4‐dihydroquinazoline dreivatives. The structures were established through pmr correlations of chemical shifts of the N‐CH 3 groups produced when the alkylating agent was methyl iodide. Spectra (uv, pmr) of known open‐chain amidines were used to confirm the structures of the isomeric dimethyl 2,4‐diphenyldihydroquinazolines. The uv spectra of 2‐phenyl‐3,4‐dihydroquinazolines possessed an absorption maximum at 320 nm while the 1,4‐dihydroanalogues had a maximum at 290 nm. Characteristic absorptions in the 1550–1650 cm −1 region of the infrared spectra also differentiated these two groups of compounds. Removal of the 2‐phenyl substituent renders these correlations less reliable.