A non-catalytic approach to the synthesis of 5,6-dihydrobenzo[ h]quinolines

Abstract

A concise synthesis of highly functionalized 5,6-dihydrobenzo[ h]quinoline-3-carbonitriles is delineated through base induced ring transformation of 4- sec-amino-2-oxo-5,6-dihydro-2 H-benzo[ h]chromene-3-carbonitriles with S-methylisothiourea sulfate and 1-carboxamidinepyrazole hydrochloride, separately, in DMF. Under analogous reaction conditions the ring transformation of 4- sec-amino-2-oxo-5,6-dihydro-2 H-benzo[ h]chromene-3-carbonitriles by formamidine acetate provided 4- sec-amino-benzo[ h]quinoline-3-carbonitriles in moderate yields, while with benzamidine hydrochloride, the reaction followed the same mechanism to yield 2-phenyl-4- sec-amino-5,6-dihydrobenzo[ h]quinoline-3-carbonitriles.