Microwave Heated Flow Synthesis of Spiro-oxindole Dihydroquinazolinone Based IRAP Inhibitors

A fast and convenient synthetic route towards spiro-oxindole dihydroquinazolinones as novel and drug-like insulin-regulated aminopeptidase (IRAP) inhibitors is reported. The synthesis is performed using a MW heated continuous flow system employing 200 mm X 3 mm i MW absorbing silicon carbide (SiC) or MW transparent borosilicate tubular reactors. A three-component MW-flow reaction to build up the spiro compounds (9 examples, 4087% yield), using the SiC reactor, as well as a SuzukiMiyaura cross-coupling reaction (71%), employing the borosilicate reactor, are presented with residence times down to 168 s. The continuous MW-flow routes provide a smooth and scalable synthetic methodology towards this class of IRAP inhibitors.