dimethyl sulfate 1) 60-70 deg C, 2 h, 2) 2-propanol, H2O, ice-salt cooling, 30 min, then rt, 1 h; Yield given. Multistep reaction. Yields of byproduct given;

sulfuric acid in tetrahydrofuran 20 h; Heating;

1: aq. H2SO4 / tetrahydrofuran / 20 h / Heating 2: DMSO, N,N'-dicyclohexylcarbodiimide, H3PO4 / 1.5 h / Ambient temperature View Scheme