The first reagent-controlled asymmetric halolactonizations. Dihydroquinidine-halogen complexes as chiral sources of positive halogen ion

The first reagent-controlled asymmetric halolactonizations are described. C omplexes of I+ with O-acyl- and O-aryldihydroquinidines are used to promote the asymmetric halolactonization of prochiral gamma,delta-unsaturated carb oxylic acids with low but measurable and reproducible enantioselectivity. E xperimental factors affecting the ee's are described.