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The first serious competitor to the known solvatochromic pyridiniumphenolate betaines has been uncovered with the 5-dimethylamino-5'-nitro-2,2'-bithiophene 1 a (X=Z=S, Y=CH, R=CH(3)), which has the added benefit of being notably sensitive to solvent in acidic media. By simple heterocyclization further compounds of the general type 1 have been synthesized, and their suitability as solvent indicators was investigated. In this way a new record was set with the selenophene analogue of 1 a.

N-Chloroacetylanthranilic acid ethyl ester reacts with potassium thiocyanate in the presence of alcohol to give the (4-oxo-3,4-dihydroquinazolin-2-ylsulfanyl)acetic acid ester (3a). In the presence of water or amines the acetic acid derivative (3b) or the acetamide derivatives (3c,d) are obtained. 2-Amino-4-oxo-3,4-dihydroquinazolines (4) arise if vigorous reaction conditions are employed.Analogously, N-chloroacetyl derivatives of 5-membered heterocycles with enaminocarbonyl structure (5,7,9,11,13, 20, 23) react with potassium thiocyanate to yield thieno[2,3-d]-, thieno[3,2-d]-, imidazo[4,5-d]-, pyrrolo[3,2-d]-, and thiazolo[4,5-d]pyrimidines (6, 8, 10, 12, 14, 21, 24). Quinazolines (18, 19) are formed from the reaction of 2-chloroacetylaminoacetophenone (16a) and 2chloroacetylaminobenzophenone (16b) with potassium thiocyanate and subsequent treatment of the intermediates with amines.In our investigations about the synthesis of quinolines and quinazolines from N-chloroacetylanthranilic acid derivatives, we continued our experimental work in order to examine the synthetic potentials of Nchloroacetylanthranilic acid ethyl esters and hetero analogues in reactions with potassium thiocyanate under various reaction conditions. In earlier publications we demonstrated that the ring closure reactions starting from N-chloroacetylanthranilic acid derivatives give access to a multitude of different substitution patterns, if the chloro atom is substituted by an aminoalkyl 1 or preferably an electron withdrawing group such as cyano, pyridinio, 2 or sulfonio. 3 Thieno[2,3-d]pyrimidines were reported to furnish various pharmacological activities. 4 With the described reaction here a new access opened up to the 2-alkylthioquinazolines and their hetero analogues. RESULTS AND DISCUSSIONN-Chloroacetylanthranilic acid ethyl ester (1) was expected to yield a quinoline derivative after substitution of the chloro atom by the thiocyanato group and subsequent ring closure reaction by Dieckmann condensation under alkaline conditions. On heating of a suspension of N-chloroacetyl-anthranilic acid ethyl ester (1) and potassium thiocyanate in acetonitrile the primary substitution product 2-thiocyanatoacetylaminobenzoic acid ethyl ester was obtained. In case that an alcohol was used as a solvent the reaction proceeded further to furnish a 4-oxo-3,4-dihydroquinazoline derivative (3). CO 2 Et NHCOCH 2 Cl CO 2 Et NHCOCH 2 SCN CO 2 Et S N NH CH 2 CH 2 NEt 2 1 2 3 3a 4 Scheme 1 70% 54 43 yields (%) 33 39 B A As described in an earlier publication, 5 we observed the same course of reaction with 2-chloroacetylaminobenzonitrile, which gave rise to 4-aminoquinazoline derivative on reaction with potassium thiocyanate in the presence of alcohol. The indicated intermediates cannot be isolated, but can be rationalized as follows (Scheme 1). The 2-iminothiazolidin-4-one intermediate was found to be isolable in the reaction of 2-chloroacetylaminoacetophenone with potassium thiocyanate. The subsequent intermediate representing a thiazolo [3,2-a] quinazoline sy...

New Synthesis of Substituted 4‐Amino‐quinazolines and Their Heteroanaloga N‐Chloracetyl‐anthranilonitriles react with potassium thiocyanate in the presence of alcohol to the (4‐aminoquinazolin‐2‐yl‐thio)‐acetic acid ester (5). In the presence of water or primary amine the acetic acid derivative (6) or the acetic acid amide derivatives (7) are obtained. 2,4‐Diaminoquinazolines (8) arise if vigorous reaction conditions are employed. With 2‐chloracetylamino‐cyclopent‐1‐en‐carbonitrile as starting material the pyrimidines (11) are formed from the reaction with potassium thiocyanate. Analogously, (4‐pyrimidyl‐2‐yl‐seleno)‐acetic acid ester (12) and (thiazolo[4,5‐d]pyrimid‐2‐yl‐seleno)‐acetic acid derivatives (16) can be prepared with potassium selenocyanate. N‐Chloracetyl derivatives of 5‐membered heterocycles with enamino‐nitrile structure (13, 15, 18, 20) react with potassium thiocyanate to yield thieno[2,3‐d]‐, thiazolo[4,5‐d]‐, pyrrolo[2,3‐d]‐, furo[2,3‐d]‐ and pyrazolo[4,3‐d]pyrimidines (14, 16, 19a, 19b, 21).

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