4-(Dimethylamino)pyridine functioned as an excellent catalyst for iodolactonization reactions of γ,δ-unsaturated carboxylic acids, affording γ-lactones, δ-lactones, or both.
The first reagent-controlled asymmetric halolactonizations are described. Complexes of I+ with O-acyl- and O-aryldihydroquinidines are used to promote the asymmetric halolactonization of prochiral θ, δ-unsaturated carboxylic acids with low but measurable and reproducible enantioselectivity. Experimental factors affecting the ee's are described. Key words: halocyclization, halogenation, halonium ions, chiral, stereoselective.