No abstract

In this work, a novel C(sp3)–C(sp2) cross-dehydrogenative-coupling method is developed to react benzoxazin-2-one derivatives with various indoles. As a result, combined use of ball milling and Fe(ii) catalysis leads to rapid coupling of 1,4-benzoxazinones with derivatives of indole. Under the conditions, derivatives of 1 couple with various indoles at room temperature to produce good yields of the desired compounds within 0.5–2 h time period. Thus, derivatives of both starting materials couple smoothly under relatively mild conditions to give good yields of 3.

N-arylation of imidazole, benzimidazole, pyrazole, and indole was performed in the presence of CuI as the catalyst and NaOH as the base in ethylene glycol medium. Apparently, ethylene glycol played a dual role as both the reaction solvent and a ligand for the catalyst. All reactions proceed selectively to give the corresponding N-arylated products. In some cases, O-alkylation or dehalogenation was observed, which was explained by the proposed catalytic cycle. Conventional heating at 120 C and microwave irradiation both were used, where the results showed that microwave irradiation could facilitate the reaction by lowering the reaction times and increasing the yields. The reaction medium was recovered and reused in several consecutive runs.

A convenient C(sp3)–C(sp3) oxidative dehydrogenative coupling reaction of 1,4-benzoxazin-2-ones with malonate esters was developed under mild conditions to obtain the respective ester malonates in high yields. Reactions take place in [omim]FeCl4, acting as both the solvent and the catalyst. Under [omim]Cl/FeCl3-DDQ conditions, derivatives of 1 coupled with malonate 2 to give the target molecules within 1–2 h time periods. The ionic liquid was recovered and reused in the next reactions without losing its efficiency.

A new method was developed for C(sp 3 )-C(sp 3 ) oxidative dehydrogenative coupling of 1,4-benzoxazin-2-ones with malonate derivatives under ball milling to obtain the respective malonate esters. Reactions take place under solvent-free conditions using FeCl2.2H2O and DDQ as the catalyst and the oxidant. Conditions are relatively mild and the target products are obtained in high yields within 3-5 h time period.