The Synthesis Of N-acylpyrrole And Quinazolin-4(3H)-ones By Cyclization

N-acylpyrrole and quinazolin-4(3H)-one compounds are widely found in biomedicine,natural products,functional materials and other important fields.Due to their superior biological activity and unique structural characteristics,such compounds play an extremely important role in these fields.Therefore,the synthesis of these compounds has attracted much attention,and become a research hotspot.With the concept of sustainable development proposed,researchers continue to explore how to use simple,efficient and mild conditions to build these two kinds of N-heterocyclic compounds.In this paper,diallylamines and 2-aminoaryloxazolines have been selected as starting materials,N-acylpyrrole and quinazolin-4(3H)-one compounds are synthesized through intramolecular cyclization reaction.The C2-alkenylation modification of N-acylpyrrole compounds can be used in the synthesis of drug intermediates.In addition,the obtained quinazolin-4(3H)-one product is further derived as corrosion inhibitor for the preliminary exploration in the mild steel corrosion protection.The detail works are described as follows:The sulfonyldiallylamines and formyldiallylamines were employed as the starting materials for the synthesis of N-sulfonylpyrroles and N-formylpyrroles,by intramolecular cyclization,using oxygen instead of tert butyl hydrogen peroxide or manganese dioxide,under the system of Grubbs second generation catalyst and catalytic equivalent copper salts(copper trifluoromethanesulfonate and copper bromide),through olefin ring-closing metathesis of diallylamines and in situ oxidative aromatization.And the highest yields were 87% and 93%,respectively.The synthesis strategy can realize the synthesis of N-acyl pyrrole compounds without using multiple equivalent strong oxidants.Meanwhile,the reactivity of substrates with different substituents has been systematically studied as well as the reaction mechanism.The N-acyl pyrrole compounds synthesized in the previous work were selected as the research object.The direct alkenylation coupling reaction of N-acylpyrroles with different terminal alkenes was occurred regioselectively at the C2-position of the pyrrole ring under ruthenium catalysis via C–H activation and using carbonyl group as a directing group.A series of N-acyl pyrrole compounds containing vinyl substituents were synthesized with the highest yield of 82%.The reaction is based on the O-weak coordination oriented group,which further expands the application range of N-acyl pyrrole compounds.Treatment of α,β-unsaturated ketones with N-acyl pyrrole under the the optimal reaction conditions could occur Michael addition to afford C2-alkylation product.In addition,the C2 alkenylation product was deprotected and hydrolyzed to obtain an intermediate compound for the synthesis of bioactive molecules.A series of quinazoline-4(3H)-ones with different substituents has been synthesized by intramolecular reaction of 2-aminoaryloxazolines in the presence of a high valent iodine reagent,[Bis(trifluoroacetoxy)iodo]benzene,and the reaction is through the free radical pathway and the coordination of aluminum trichloride.Meanwhile,a series of dibenzamides has been synthesized in the presence of aluminum trichloride.The reaction is simple,mild,time-consuming and without using transition metal catalysts,which can be an efficient and novel method for the synthesis of quinazoline-4(3H)-one derivatives.After introducing piperazine heterocycles into the synthesized quinazoline-4(3H)-one product,we synthesized a corrosion inhibitor for the corrosion protection of mild steel in 1.0 M HCl medium.The corrosion inhibition performance of this compound was evaluated by electrochemical,weight loss,scanning electron microscopy and X-ray photoelectron spectroscopy.The electrochemical,weight loss and scanning electron microscopy results show the quinazoline-4(3H)-one derivative with piperazine heterocycle has good corrosion inhibition performance.And the corrosion inhibition efficiency can be increased to 96.6% at 0.4 m M by calculation.This study can be used as a preliminary exploration of this type of skeleton corrosion inhibitor in the mild steel corrosion protection.And it also provides an effective and practical way for the synthesis of new organic compounds,which can be applied in the field of corrosion inhibitors.