Abstract A small library of hitherto unprepared pyrazolo [3, 4-d]-4, 5-dihydropyrimidin-6-ones was synthesized on a preparative scale. The synthesis starts with a substituted 5- aminopyrazole that reacts with an isocyanate to give the corresponding urea. The latter undergoes a chlorotrimethylsilane-promoted [5+ 1] cyclocondensation with an aldehyde yielding the title pyrazolo [3, 4-d]-4, 5-dihydropyrimidin-6-one. Both synthetic steps are ...
