3 A molecular sieve; ammonium formate; sodium cyanoborohydride in methanol T=20°C; Cyclization; reduction; 24 h;

lithium aluminium tetrahydride

1.1: DMSO; TFAA / CH2Cl2 / 2 h / -78 °C 1.2: 71 percent / Et3N / CH2Cl2 / 1 h / -78 - 20 °C 2.1: 32 percent / NaBH3CN; HCO2NH4; molecular sieves (3A) / methanol / 24 h / 20 °C View Scheme

1.1: diisobutylaluminium hydride / diethyl ether / 1 h / 0 °C / |Inert atmosphere 1.2: 25 h / -78 °C / |Inert atmosphere 2.1: thionyl chloride / ethylene glycol dimethyl ether / 3 h / 0 - 25 °C 2.2: 4 h / 0 - 25 °C View Scheme