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Lithiation of 2-alkyl-3-amino- and 2-alkyl-3-(methylamino)-4(3H)-quinazolinones

Smith, Keith, El-Hiti, Gamal A., Abdel-Megeed, Mohamed F. and Abdo, Mohamed A. 1996. Lithiation of 2-alkyl-3-amino- and 2-alkyl-3-(methylamino)-4(3H)-quinazolinones. Journal of organic chemistry 61 (2) , pp. 656-661. 10.1021/jo950989l

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Abstract

3-Amino-2-methyl-4(3H)-quinazolinone has been doubly lithiated, on nitrogen and in the 2-methyl group, with n-butyllithium. The lithium reagent thus obtained reacts with a variety of electrophiles (D2O, benzophenone, cyclohexanone, cyclopentanone, acetophenone, benzaldehyde, tetraisopropylthiuram disulfide (TITD)) to give the corresponding 2-substituted derivatives in very good yields. Reactions of the dilithio reagent with 2 molar equiv of methyl iodide or phenyl isocyanate give disubstituted derivatives. Double lithiation of the 2-ethyl and 2-propyl analogues have been achieved using LDA, and subsequent reactions with most electophiles are then similar. In the reaction of the dianion of the 2-ethyl compound with TITD, deamination from position 3 takes place with the formation of the 2-substituted derivative. In reactions with prochiral ketones, the dianion of the 2-ethyl compound gives very high diastereoselectivity. Lithiation and subsequent reactions of 3-(methylamino) analogues take place in a similar manner, thus providing access to a range of substituted 3-(methylamino)-2-alkyl-4(3H)-quinazolinones by a general procedure. Lithiation of 3-(dimethylamino)-2-ethyl-4(3H)-quinazolinone did not take place under similar conditions. Lithiation of 3-amino-2-unsubstituted-4(3H)-quinazolinone was also unsuccessful.

Item Type: Article
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: American Chemical Society
ISSN: 0022-3263
Last Modified: 04 Jun 2017 02:51
URI: http://orca.cf.ac.uk/id/eprint/12731

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