Triphenylphosphine (577 mg, 2.20 mmol), di-tert-butylazodicarboxylate (506 mg, 2.20 mmol) and tert-butyl 4-hydroxy-piperidine-1-carboxylate (1.32 g, 6.62 mmol) are taken up in 6 mL THF, stirred for 15 min at 20° C. and then combined with 6-bromo-2-chloro-quinazolin-8-ol (1.16 g, 4.45 mmol). After stirring for 24 h at 20° C. the mixture is diluted with MeOH, the solvent is eliminated in vacuo, the crude product is purified by RP-chromatography (method prep. HPLC1; 20% acetonitrile to 90% in 6 min) and tert-butyl 4-(6-bromo-2-chloro-quinazolin-8-yloxy)-piperidine-1-carboxylate (HPLC-MS: tRet.=1.99 min; method FECB5) is obtained.
