1: molecular sieves (4 Angstroem), BF3*OEt2 / diethyl ether / 0.5 h 2: 1.) 1,1,1,3,3,3,-hexamethyldisilazane, ammonium sulfate, 2.) SnCl4, TMSOTf / 1.) reflux, 2 h, 2.) 1,2-dichloroethane, RT, 2 h 3: TBAF / tetrahydrofuran / 8 h 4: K2CO3 / methanol View Scheme

1: CCl4, tris(dimethylamino)phosphane / tetrahydrofuran / 4 h / -80 °C 2: 1.) KOH, tris<2-(2-methoxyethoxy)ethyl>amine (TDA-1) / 1.) MeCN, r.t., 2.) THF, 10 min. 3: 93 percent / Bu4NF / tetrahydrofuran / 0.25 h / Ambient temperature 4: 1,) hydrazine hydrate, 2.) Raney-Ni / 1.) 120-130 deg C, 90 min., 2.) ethanol, 2 h, heating View Scheme

1: tris(dimethylamino)phosphane, CCl4 / tetrahydrofuran; CCl4 / 2 h / -78 °C 2: 1) tris<2-(2-methoxyethoxy)ethyl>amine, K2CO3 / 1) acetonitrile, room temp., 50 min; 2) acetonitrile, room temp., 60 min 3: 72 percent / Raney-Ni / methanol; dioxane / Ambient temperature 4: 85 percent / Bu4NF / tetrahydrofuran / 2 h / Ambient temperature 5: 1) POCl3; 2) (Bu3NH)4P2O7, Bu3N / 1) PO(OMe)3, 4 deg C, 3 h; 2) DMF, 0 deg C, 1 min View Scheme

1: molecular sieves (4 Angstroem), BF3*OEt2 / diethyl ether / 0.5 h 2: 1.) 1,1,1,3,3,3-heksamethylenedisilazane, ammonium sulfate, 2.) SnCl4, TMSOTf / 1.) reflux, 2 h, 2.) 1,2-dichloroethane, RT, 2 h 3: TBAF / tetrahydrofuran / 8 h / Ambient temperature View Scheme

1: molecular sieves (4 Angstroem), BF3*OEt2 / diethyl ether / 0.5 h 2: 1.) 1,1,1,3,3,3,-hexamethyldisilazane, ammonium sulfate, 2.) SnCl4, TMSOTf / 1.) reflux, 2 h, 2.) 1,2-dichloroethane, RT, 2 h 3: TBAF / tetrahydrofuran / 8 h / Ambient temperature View Scheme

1: tris(dimethylamino)phosphane, CCl4 / tetrahydrofuran; CCl4 / 2 h / -78 °C 2: 1) tris<2-(2-methoxyethoxy)ethyl>amine, K2CO3 / 1) acetonitrile, room temp., 50 min; 2) acetonitrile, room temp., 60 min 3: 79 percent / Bu4NF / tetrahydrofuran / 2 h / Ambient temperature 4: 1) POCl3; 2) (Bu3NH)4P2O7, Bu3N / 1) PO(OMe)3, 4 deg C, 3 h; 2) DMF, 0 deg C, 1 min View Scheme