Research on heterocyclic compounds, XLI. 2-Phenylimidazo

A substrate-dependent reaction of 1-aryl-2-alkyl-1,2-diketones with 2-aroyl-1-chlorocyclopropanecarboxylates: selective access to 2',5'-dicyclopropoxy-1,1':4',1''-teraryls and pentafulvenes

An interesting substrate-controlled one-pot approach to highly substituted 2',5'-dicyclopropoxy-1,1':4',1''-teraryls and 6-hydroxypentafulvenes involving various 1,2-diketones and 2-aroyl-1-chlorocyclopropanecarboxylates as 3C Michael acceptors triggered by Cs₂CO₃ has been developed. We noticed that 1,2-diketones play a decisive role in this reaction to determine the product's selectivity. For example, aryl rings having electron-poor functionalities at the para and meta-positions of 1,2-diketones led to 2,5-diarylhydroquinones selectively via a cyclodimerization/double oxa-Michael process with highly strained cyclopropenes. However, when 1-naphthyl/electron-donating aryl/ortho-aryl-substituted 1,2-diketones were chosen, the Michael-initiated ring expansion reaction (C-C and CC bonds) took place under the same conditions that gave the corresponding pentafulvenes predominately. Moreover, this reaction has several imperative features such as good to high diastereoselectivities, wide substrate scope, good functional group tolerance, transition metal-free process, etc.

Two Efficient One-Pot Approaches for Regioselective Synthesis of New 3-Arylpyridazino[4,3-c]quinolin-5(6H)-ones

Two efficient regioselective approaches for the one-pot synthesis of 3-arylpyridazino[4,3-c]quinolin-5(6H)-one derivatives are reported, by the three-component reaction of arylglyoxal monohydrates, quinoline-2,4-diol, and hydrazinium dihydrochloride or hydrazine hydrate in ethanol and pyridine. In ethanol, the reactions were catalyzed by 1,4-diazobicyclo[2,2,2]octane. The features of both procedures are high regioselectivity, mild reaction conditions, good to high yields, and operational simplicity.