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Three- component reactions of 1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone, aldehydes and malononitrile or ethyl cyanoacetate in the presence of nanoparticles of ZnO as catalyst are explained as effective and green synthetic method for generating 9H- furo[2,3-f]chromenes in good yield.

It is a well-known fact that by changing the 1,3-dipolar cycloaddition (1,3-DC) reaction mechanism from concerted to stepwise, the stereospecificity is lost; since in synthesizing the required heterocyclic molecules that reaction is a requisite, it is important to study the concertedness of that reaction. Several papers on this subject have already stated that the existence of electron withdrawing groups (EWG) or electron donor groups (EDG) on dipole or dipolarophile leads to a high-energy differentiation between the dipole HOMO and dipolarophile LUMO (or vice versa) as well as the emergence of an intermediate in the reaction pathway. This paper seeks answering the question of when an EWG on dipole and an EDG on dipolarophile could be a factor in making the reaction mechanism stepwise, and does repositioning of functional groups in replacing dipole and dipolarophile switches the reaction mechanism from stepwise into concerted or vice versa?

The order of reaction, especially in 1,3-dipolar cycloadditions directly affects the products' stereo selectivity. Due to this fact that a wide range of heterocyclic rings of natural products and biologically active molecules are synthesizing via this valuable procedure, understanding about the order of this reaction is so useful in designing the synthesis of different types of heterocyclic species. Therefore, the order of 1, 3-dipolar reaction has been carefully studied by many researchers but it seems that this question is still open despite many valuable answers. Considering this, in the present work, it is attempted to pursue this subject by theoretical investigation of any possible pathway of 1, 3-dipolar reaction of tetra amino ethylene as a highly electron rich dipolarophile and trifluoro methyl azide as an electron poor 1,3-dipole. During the calculations, one, two, and three step mechanism(s) have been found to be possible for the present 1, 3-dipolar reaction.