Chiral organochlorosilanes derived from terpenes: diastereoselective hydrosilylation of methylene bicyclo[2.2.1]heptanes with HSiMenCln-2 (n=0-2)

The H₂PtCl₆ catalysed hydrosilylation of the terpenes (+)-α-fenchene (<b>XI</b>), (−)-2-methylene bornane (<b>XII</b>), (+)-camphene (<b>XIII</b>) and (−)-3-methylene fenchane (<b>XIV</b>) using HSiMe₂Cl or HSiMeCl₂ proceeds with high regioselectively and in some cases, with high diastereoselectivity. KF-assisted oxidation of the hydrosilylation products gives predominately <i>endo</i>-terpene alcohols. The alcohols have inverted <i>endo/exo</i> ratios to those formed by oxidative hydroboration. Reaction of <b>XIV</b> with HSiMe₂Cl or HSiMeCl₂ is accompanied by a clean rearrangement of the isocamphane skeleton into (+)-2-methylene bornane (<b>XII</b>) prior to hydrosilylation.<br><br>The hydrosilylation of α-fenchene, 2-methylene bornane, camphene and 3-methylene fenchane with chlorosilanes HSiMe<i>_n</i>Cl<i>_n</i>− 2 (<i>n</i>=0–2) occurred with varying degrees of diastereoselectivity providing anti-Markovnikov product mixtures, in which the <i>endo</i>-isomers dominate over the <i>exo</i>-isomers. These mixtures were oxidized to give the corresponding terpene alcohols. 3-Methylene fenchane undergoes a rearrangement into 2-methylene bornane prior to hydrosilylation.<br><br>