NMR determination of enantiomers of 7‐chloro‐3,3a‐dihydro‐2‐methyl‐2H,9H‐isoxazolo[3,2‐b][1,3]benzoxazin‐9‐one using chiral shift reagent, tris[3‐(heptafluorobutyryl)‐d‐camphorato]europium(III)