Controllable Site-Selective Construction of 2-and 4-Substituted Pyrimido[1,2-b]indazole from 3-Aminoindazoles and Ynals

A straightforward and novel controllable siteselective construction of 2- and 4-substituted pyrimido[1,2-b]indazole from 3-aminoindazoles and ynals has been developed. The high regioselectivity of this reaction could be easily switched by converting different catalytic systems. In this way, a series of 2- and 4-substituted pyrimido[1,2-b]indazole derivatives were obtained in moderate to good yields. In addition, the photophysical properties of compound 3a prepared by the present method were discussed.

Automated summary

A novel controllable synthesis method has been developed for constructing 2- and 4-substituted pyrimido[1,2-b]indazoles from 3-aminoindazoles and ynals. The regioselectivity of the reaction can be easily switched by converting different catalytic systems, resulting in moderate to good yields of the desired derivatives. The photophysical properties of compound 3a prepared by this method were also discussed.