Contrary to a number of reports, alkylations of the privileged 3, 4-dihydroquinazoline scaffold provide N3-alkylated products, and not 4-alkoxyquinazolines. To correctly assign the structure, 13C NMR shifts of the–Z–CHn–(Z= O, N) fragment are necessary; resonances in the 45–55 ppm range are indicative of N3-alkylation. Treatment of 3, 4-dihydroquinazoline-4- one with p-TsCl afforded the N3-tosylated compound, whose reaction with an amine ...
