1: Ti(OiPr)4, Me3SiN3 / benzene 2: 91 percent / NEt3, 4-dimethylaminopyridine (DMAP) / CH2Cl2 3: (CH3)3SiOTf / 1,2-dichloro-ethane 4: NaOH / methanol 5: 4.7 N H2SO4 / methanol View Scheme