Uses of cyclohexane-1,3-dione for the synthesis of 1,2,4-triazine derivatives as anti-proliferative agents and tyrosine kinases inhibitors.

Tetrahydrobenzo[b]thiophene derivatives were well known to be biologically active compounds and many of them occupy a wide range as anticancer agent drugs. One of our main aim of this work was to synthesize target molecules not only possess anti-tumor activities but also kinase inhibitors. To achieve this goal, our strategy was to synthesize a series of novel 1,2,4-triazines as efficient anticancer drugs with low cytotoxicity and good bioavailability properties using cyclohexane-1,3-dione and 3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophene-2-diazonium chloride to give the 2-(2-(2,6-dioxocyclohexylidene)hydrazinyl)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile (3) as the key starting material for many heterocyclization reactions. Compound 3 was reacted with phenylisothiocyanate to give the tetrahydrobenzo[e][1,2,4]triazine derivative 5 which reacted with hydrazines to give dihydrazone derivatives. In addition, it underwent multi-component reactions with aromatic aldehydes and either malononitrile or ethyl cyanoacetate in the presence of triethylamine or ammonium acetate to produce fused pyran and fused pyridine derivatives, respectively. Compounds obtained in this work were evaluated for their c-Met kinase inhibitory potency as well as in-vitro cytotoxic activity against the six typical cancer cell lines (A549, H460, HT-29, MKN-45, U87MG, and SMMC-7721). Molecular modeling studies were carried out for the most active compounds 5, 7a, 7b, 10c, 10e, 11c and 11f using Molecular Operating Environment (MOE) software. It was found that all the tested compounds displayed potent c-Met enzymatic activity with IC values ranging from 0.24 to 9.36 nM. Ten of them (5, 7a, 7b, 10c, 10e, 10f, 11b, 11c, 11d and 11f) exhibited higher potency with IC values less than 1.00 nM compared with foretinib (IC = 1.16 nM). Also those compounds possessed moderate to strong cytotoxicity against the six tested cancer cell lines in the single-digit µM range. The synthesized compounds 5, 7a, 7b, 10c, 10e, 11c and 11f were fit on the active site of c-Met kinase, with almost the same binding pattern as foretinib and higher binding energy scores (from -16.38 to -18.21 kcal/mol) compared to foretinib (-16.37 kcal/mol). A series of novel 1,2,4-triazines were synthesized and displayed potent bioactivities, indicating that these compounds could be considered as a new lead for more investigation in the future.