Synthesis of Substituted Pyrimido[1,2‐b]indazoles through (3+2+1) Cyclization of 3‐Aminoindazoles, Ketones, and N,N‐Dimethylaminoethanol as One‐Carbon Synthon

2‐Mono‐ or 2,3‐disubstituted pyrimido[1,2‐b]indazoles are synthesized by a (3+2+1) three‐component cyclization of 3‐aminoindazoles, ketones, and N,N‐dimethylaminoethanol as a methine source. The reaction demonstrates good tolerance of both aromatic and aliphatic ketones, as well as various substitution patterns in air. A plausible mechanism is discussed.