active ▁elect roph iles ▁under go ▁reduction , ▁select ivity ▁is ▁possible ▁in ▁re actions ▁of ▁substr ates ▁with ▁multiple ▁redu cible ▁functional ▁groups . ▁Ch iral ▁Lewis ▁ac ids ▁and ▁metal ▁complex es ▁may ▁be ▁used ▁for ▁the ▁en ant io select ive ▁reduction ▁of ▁k et ones ▁with ▁hyd ros il anes . ▁( 1 ) ▁ ▁H yd ros il anes ▁are ▁not ▁intr ins ically ▁nucle oph il ic ; ▁thus , ▁they ▁react ▁only ▁with ▁highly ▁elect roph il ic ▁functional ▁groups ▁that ▁have ▁car b ocation ic ▁character . ▁However , ▁many ▁reson ance - st abil ized ▁car b oc ations ▁are ▁ins u fficient ly ▁elect roph il ic ▁to ▁react ▁with ▁hyd ros il anes . ▁Upon ▁the ▁generation ▁of ▁a ▁car b ocation , ▁rate - det erm ining ▁hyd ride ▁transfer ▁from ▁the ▁organ os il ane ▁occurs ▁to ▁yield ▁a ▁reduced ▁product ▁and ▁a ▁neutral ▁sil ane ▁in ▁which ▁the ▁counter ion ▁of ▁the ▁car b ocation ▁has ▁replaced ▁hydro gen . ▁Prior ▁to ▁hyd ride ▁transfer , ▁the ▁car b ocation ▁intermediate ▁is ▁li able ▁to ▁under go ▁Wagner - Me er we in ▁re arr ang ements . ▁ ▁This ▁simple ▁picture ▁is ▁complicated ▁by ▁experimental ▁observations ▁that ▁point ▁to ▁more ▁complex ▁mechan isms . ▁For ▁instance , ▁ret ention ▁of ▁configuration ▁at ▁sil icon ▁has ▁been ▁observed ▁in ▁sil ane ▁redu ctions ▁of ▁ch iral ▁tri ary l ▁m eth yl ▁ch lor ides ▁in ▁ben z ene