The [(2-aminobenzoyl)amino]alkanoic acids and their esters 1 showed a different reaction behaviour with diethyl oxalate. Compound 1 (n = 2,3) was converted into the quinazolinylalkanoates 3. o-Aminohippurate yielded with ethyl (chloroformy1)formate a mixture of the amide 4 and the cyclized quinazolinone 7b. Ethyl 3,4-dihydro-4-oxoquinazoline-2-carboxylate (6) reacted with 2-bromoalkanoates, in the presence of NaH, to the [2-(ethoxycarbonyl)-3,4-dihydro-4-oxoquinazolin-3-yl]acetates 7 in the case of alkyl bromoacetate, and to the 0-alkylated derivatives 8 with the ethyl 2-bromopropionate and -butyrate. 2-Aminobenzamide (5) gave with ethyl 3-(chloroforrnyl)-2-propenoate and methyl 3-(ch1oroformyl)propionate the amides 9 or 11, respectively, and not the expected quinazolinones. The cyclized product I2 was obtained from 11 and ethyl bromoacetate. Tetrahydroquinazolin-4(3H)-thione 14 was synthesized by the reaction of 13 with NH,, and it was alkylated at the S-atom with bromoalkanoates to 15. The hydrazide 16 was synthesized from 15b with hydrazine hydrate.Einleitung. -Unser Interesse galt der Synthese von Chinazolinonen, die in 2-Stellung durch eine Carboxyl-Gruppe und in 3-Stellung durch eine Alkansaure substituiert sind.

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Es wird gezeigt, daß die polarographische Bestimmung von Nb mindestens in 10n HCl durchgeführt werden muß.

Mit der Titelmethode läßt sich Nb(V) in 12m H2SO4 in Gegenwart von Mo(VI) bestimmen.

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