1: p-toluenesulfonic acid / toluene / 18 h / Heating 2: cyclohexane; diethyl ether; toluene / 1) 0 deg C, 0.5 h, 2) r.t., 1.5 h 3: CHCl3 / 360 h / Heating 4: 1) 1-chloroethyl chloroformate, 2) MeOH / 1) 1,2-dichloroethane, a) 0 deg C, 15 min, b) reflux, 2 h, 2) reflux, 4 h View Scheme

1: cyclohexane; diethyl ether; toluene / 1) 0 deg C, 0.5 h, 2) r.t., 1.5 h 2: CHCl3 / 360 h / Heating 3: 1) 1-chloroethyl chloroformate, 2) MeOH / 1) 1,2-dichloroethane, a) 0 deg C, 15 min, b) reflux, 2 h, 2) reflux, 4 h View Scheme

1: p-toluenesulfonic acid / toluene / 18 h / Heating 2: cyclohexane; diethyl ether; toluene / 1) 0 deg C, 0.5 h, 2) r.t., 1.5 h 3: CHCl3 / 360 h / Heating 4: 1) 1-chloroethyl chloroformate, 2) MeOH / 1) 1,2-dichloroethane, a) 0 deg C, 15 min, b) reflux, 2 h, 2) reflux, 4 h View Scheme

1: CHCl3 / 360 h / Heating 2: 1) 1-chloroethyl chloroformate, 2) MeOH / 1) 1,2-dichloroethane, a) 0 deg C, 15 min, b) reflux, 2 h, 2) reflux, 4 h View Scheme