Nitroaromatics In [3+2]-cycloaddition And C(sp~3)-H Bond Arylation

Oxadiazole compounds and triarylmethanol compounds have attracted considerable attention due to their widespread presence in a large number of natural products and biologically active moleculars.So far,the methods for the synthesis of these compounds are limited.The traditional methods for the synthesis of 1,2,4-oxadiazole compounds depended on 1,3-dipolar cycloaddition of nitrile with nitrile oxide,while triarylmethanol compounds were prepared by adding organolithium or Grignard reagent to diaryl ketone.However,these methods suffer from drawbacks such as poor substrate tolerance or contain organometallic reagents that are difficult to remove.Therefore,it is particularly important to develop a more mild,environmentally friendly,and practical method for the synthesis of these compounds.Using nitroaromatics as starting material,we reported two new protocols for the synthesis of1,2,4-oxadiazole and triarylmethanol via[3+2]-cycloaddition and C(sp~3)-H bond arylation reactions.The present study mainly includes the following three aspects:1.Synthesis of 2,5-dihydro-1,2,4-oxadiazole compounds with aldimines:firstly,aldimines were prepared according to reported literature,subsequently,aldimines reacted with nitroaromatics to generate[3+2]-cycloaddition reaction,and finally more than 50 2,5-dihydro-1,2,4-oxadiazoles were prepared(up to 95%yield).2.Preparation of triarylmethane deraivatives with diarylmethane:firstly,diarylmethane derivatives were prepared,these substrates next underwent tandem arylation/oxidation reaction to give triarylmethanol.Finally,more than 30 triarylmethanol compounds were prepared,(up to 92%yield).3.Synthesis of tetraarylmethane compounds with triarylmethane:Based on the synthesis mechanism of triarylmethanes,we use triarylmethanes instead of diarylmethanes to undergo arylation reaction to give tetrarylmethanes with spherical structure.Furthermore,more than 25 tetrarylmethanes were prepared.