▁and ▁is ▁able ▁to ▁couple ▁a ▁wide ▁range ▁of ▁materials ▁in ▁good ▁to ▁excellent ▁yields . ▁ ▁In ▁catal ysis ▁Ph osph ino ox az ol ines ▁are ▁able ▁to ▁influence ▁both ▁the ▁en ant io select ivity ▁and ▁reg io select ivity ▁of ▁a ▁range ▁of ▁metal ▁catal ys ed ▁re actions . ▁In ▁re actions ▁involving ▁symmetric ▁transition ▁states ▁these ▁properties ▁work ▁in ▁concert ▁to ▁indu ce ▁asym met ry ▁and ▁thus ▁promote ▁the ▁formation ▁of ▁a ▁single ▁product . ▁En ant io select ivity ▁is ▁controlled ▁by ▁the ▁ch ir ality ▁of ▁the ▁lig and ▁which ▁is ▁normally ▁located ▁on ▁the ▁ox az oline ▁ring , ▁however ▁the ▁P - cent re ▁may ▁also ▁be ▁s tere ogen ic . ▁Reg io select ivity ▁is ▁controlled ▁by ▁variety ▁of ▁ster ic ▁and ▁electronic ▁factors ▁the ▁most ▁important ▁of ▁which ▁being ▁a ▁form ▁of ▁trans ▁effect , ▁in ▁which ▁atoms ▁complex ed ▁trans ▁to ▁the ▁P ‑ atom ▁become ▁more ▁elect roph il ic ▁than ▁ones ▁located ▁trans ▁to ▁the ▁N ‑ atom . ▁This ▁is ▁caused ▁by ▁the ▁P ‑ atom ▁eng aging ▁in ▁back ▁bond ing , ▁as ▁it ▁is ▁a ▁ π ‑ elect ron ▁accept or . ▁ ▁Al ly lic ▁substitution s ▁ ▁Ph osph ino ox az ol ines ▁are ▁used ▁as ▁lig ands ▁in ▁al ly lic ▁substitution ▁re actions ▁as ▁both ▁en ant io - ▁and ▁reg io select ivity ▁is ▁required ▁to ▁give ▁an ▁en anti omer ically ▁pure ▁product ▁due ▁to