1: 1) LDA / 1) hexane, THF, 0 deg C, 30 min, 2) HMPA, -78 deg C -> 0 deg C, 1 h 2: 1) Mg / 1) diethyl ether, 2) rt, 2 h 3: BF3*Et2O / CH2Cl2 / 0.5 h / -78 °C 4: 87 percent / MnO2 / various solvent(s) / 36 h / 180 °C 5: 53 percent / DDQ / benzene / 4.7 h / Heating 6: 1) 10 M BH3*SMe2, 2) 10percent aq. NaOH, 30percent aq. H2O2 / 1) THF, 0 deg C, 1 h, 2) rt, 6 h 7: 94 percent / oxalyl chloride, DMSO, NEt3 / CH2Cl2 / -78 °C 8: 35 percent / KMnO4, MgSO4 / acetone / 2 h View Scheme

1: 1) LDA / 1) hexane, THF, 0 deg C, 30 min, 2) HMPA, -78 deg C -> 0 deg C, 1 h 2: 1) Mg / 1) diethyl ether, 2) rt, 2 h 3: BF3*Et2O / CH2Cl2 / 0.5 h / -78 °C 4: 87 percent / MnO2 / various solvent(s) / 36 h / 180 °C 5: 53 percent / DDQ / benzene / 4.7 h / Heating 6: 1) 10 M BH3*SMe2, 2) 10percent aq. NaOH, 30percent aq. H2O2 / 1) THF, 0 deg C, 1 h, 2) rt, 6 h 7: 94 percent / oxalyl chloride, DMSO, NEt3 / CH2Cl2 / -78 °C 8: 50 percent / KMnO4, MgSO4 / acetone / 2 h View Scheme

1: 1) LDA / 1) hexane, THF, 0 deg C, 30 min, 2) HMPA, -78 deg C -> 0 deg C, 1 h 2: 1) Mg / 1) diethyl ether, 2) rt, 2 h 3: BF3*Et2O / CH2Cl2 / 0.5 h / -78 °C 4: 87 percent / MnO2 / various solvent(s) / 36 h / 180 °C 5: 53 percent / DDQ / benzene / 4.7 h / Heating View Scheme

1: 1) LDA / 1) hexane, THF, 0 deg C, 30 min, 2) HMPA, -78 deg C -> 0 deg C, 1 h 2: 1) Mg / 1) diethyl ether, 2) rt, 2 h 3: BF3*Et2O / CH2Cl2 / 0.5 h / -78 °C 4: 66 percent / MnO2 / various solvent(s) / 20 h / 180 °C / other dihydrobenzocyclobutenes View Scheme

potassium hydroxide in ethanol; water T=100°C; 5 h;

1: 1) LDA / 1) hexane, THF, 0 deg C, 30 min, 2) HMPA, -78 deg C -> 0 deg C, 1 h 2: 1) Mg / 1) diethyl ether, 2) rt, 2 h 3: BF3*Et2O / CH2Cl2 / 0.5 h / -78 °C 4: 87 percent / MnO2 / various solvent(s) / 36 h / 180 °C 5: 53 percent / DDQ / benzene / 4.7 h / Heating 6: 1) 10 M BH3*SMe2, 2) 10percent aq. NaOH, 30percent aq. H2O2 / 1) THF, 0 deg C, 1 h, 2) rt, 6 h View Scheme

1: 1) LDA / 1) hexane, THF, 0 deg C, 30 min, 2) HMPA, -78 deg C -> 0 deg C, 1 h 2: 1) Mg / 1) diethyl ether, 2) rt, 2 h 3: BF3*Et2O / CH2Cl2 / 0.5 h / -78 °C 4: 87 percent / MnO2 / various solvent(s) / 36 h / 180 °C 5: 53 percent / DDQ / benzene / 4.7 h / Heating 6: 1) 10 M BH3*SMe2, 2) 10percent aq. NaOH, 30percent aq. H2O2 / 1) THF, 0 deg C, 1 h, 2) rt, 6 h 7: 94 percent / oxalyl chloride, DMSO, NEt3 / CH2Cl2 / -78 °C View Scheme

1: 1) LDA / 1) hexane, THF, 0 deg C, 30 min, 2) HMPA, -78 deg C -> 0 deg C, 1 h 2: 1) Mg / 1) diethyl ether, 2) rt, 2 h 3: BF3*Et2O / CH2Cl2 / 0.5 h / -78 °C 4: 97 percent / MnO2 / various solvent(s) / 24 h / 180 °C View Scheme