N,N,N',N,-tetramethylethylenediamine; sec.-butyllithium in diethyl ether; cyclohexane -70 deg C, 0.5 h; 0 deg C, 1 h;

1: 1.) n-BuLi / 1.) THF, hexane, -23 deg C, 30 min, 2.) 6 deg C, 17 h 2: 1.) n-BuLi, 2.) HMPA / 1.) THF, hexane, 15 min, 2.) -78 deg C, 4 h 3: 92 percent / NaI / butan-2-one / 46 h / 4 °C 4: 1.) n-BuLi / 1.) THF, hexane, -23 deg C, 20 min, 2.) -23 deg C, 30 min 5: sec-BuLi, TMEDA / tetrahydrofuran; cyclohexane / 0.5 h / -78 °C / single and double ring-closure reactions of dianions of bis(diphenyl thioacetals), carbene generation and intramolecular capture, mechanistic study View Scheme

1: 92 percent / NaI / butan-2-one / 46 h / 4 °C 2: 1.) n-BuLi / 1.) THF, hexane, -23 deg C, 20 min, 2.) -23 deg C, 30 min 3: sec-BuLi, TMEDA / tetrahydrofuran; cyclohexane / 0.5 h / -78 °C / single and double ring-closure reactions of dianions of bis(diphenyl thioacetals), carbene generation and intramolecular capture, mechanistic study View Scheme

1: 1.) n-BuLi / 1.) THF, hexane, -23 deg C, 20 min, 2.) -23 deg C, 30 min 2: sec-BuLi, TMEDA / tetrahydrofuran; cyclohexane / 0.5 h / -78 °C / single and double ring-closure reactions of dianions of bis(diphenyl thioacetals), carbene generation and intramolecular capture, mechanistic study View Scheme

N,N,N',N,-tetramethylethylenediamine; sec.-butyllithium in tetrahydrofuran; cyclohexane T=-78°C; 0.5 h; Yield given. Yields of byproduct given;

Yield given. Multistep reaction. Yields of byproduct given;

1: 53 percent / glacial acetic acid, aq. hydrogen peroxide / 8 h / 90 - 100 °C 2: 68 percent / 0.02 h / Heating View Scheme