1: in tetrahydrofuran 1 h; Molecular sieves; 2: With sodium tris(acetoxy)borohydride in tetrahydrofuran 24 h;

sodium tetrahydroborate; chloro-trimethyl-silane in tetrahydrofuran T=20°C; 66 h; Heating / reflux;

1.1: 64 percent / H2O; HCl / diethyl ether / 72 h 2.1: sodium borohydride; chlorotrimethylsilane / tetrahydrofuran / 64 h / Heating 2.2: HCl; ammonium chloride / tetrahydrofuran; methanol; H2O / 20 °C View Scheme

1.1: n-butyllithium; TMEDA / hexane; tetrahydrofuran / 0.92 h / -78 °C 1.2: 40 percent / hexane; tetrahydrofuran / 2.25 h 2.1: 64 percent / H2O; HCl / diethyl ether / 72 h 3.1: sodium borohydride; chlorotrimethylsilane / tetrahydrofuran / 64 h / Heating 3.2: HCl; ammonium chloride / tetrahydrofuran; methanol; H2O / 20 °C View Scheme

in toluene stirring of the boroxine with diisopropylamine in toluene at room temp.for 15 h; heating at 70°C for 1 h;; filtration; evapn. of the filtrate; drying under vac.; recrystn. from benzene; elem. anal.;;

1: tetramethylethylenediamine; n-butyllithium / tetrahydrofuran; hexane 2: HCl / water; diethyl ether 3: chlorotrimethylsilane / tetrahydrofuran View Scheme

1: HCl / water; diethyl ether 2: chlorotrimethylsilane / tetrahydrofuran View Scheme

1: HCl / water; diethyl ether 2: chlorotrimethylsilane / tetrahydrofuran View Scheme

chlorotrimethylsilane in tetrahydrofuran byproducts: H2; to stirred suspn. of NaBH4 in THF under Ar wa added ClSiMe3; mixt. heated at reflux for 2 h; cooled to room temp.; pinacol ester added as suspn.in THF; mixt. heated at reflux for 64 h; cooled to room temp.; mixt. quenched (MeOH) over 30 min followed by H2O;solvent partially evapd.; satd. aq. NH4Cl added; 3 M HCl added to pH 1 of aq. layer; CH2Cl2 added; pH adjusted to 9 (Na2CO3) with stirring; sep d.; aq. layer was re-extd. (CH2Cl2)..;