STEREOCHEMICAL CONSEQUENCES OF METHOXYL PARTICIPATION . ABSOLUTE CONFIGURATION OF 2-CHLORO-5-METHOXYPENTANE

The absolute configuration of 2-chloro-5-methoxypentane has been determined by the following sequence: (S)-(+)-5-hexen-2-ol (absolute configuration known) (R)-(—)-5-chloro-1-hexene (with inversion) → (R)-(—)- 4-chloro-1-pentanol → (R)-(—)-2-chloro-5-methoxypentane. The replacement of hydroxyl by chlorine using triphenylphosphine in refluxing carbon tetrachloride was shown to proceed mainly with inversion. The proof of configuration of 2-chloro-5-methoxypentane shows that lithium chloride in pyridine reacts with 5-methoxy-2-pentyl brosylate partly by direct Sn2 displacement and partly through an intermediate methoxonium ion. © 1968, American Chemical Society. All rights reserved.