Stereochemistry and regiochemistry of the addition of lodonium nitrate to alkenes

Abstract

Iodonium nitrate in the presence of pyridine adds trans-stereospecifically and regiospecifically to a series ofZ–E pairs of alkenes to give iodoalkyl nitrate esters and iodoalkyl pyridinium nitrates. The stereochemistry of the products was confirmed by relating them chemically with known compounds. Addition to the less hindered (Z)-[β-²H]styrene is also stereospecific, eliminating the possibility of restricted rotation during addition. Ring closure by neighbouring sulphur in the addition of iodonium nitrate to 1-allyl-3,3-diethylthiourea affords a thiazole. The failure to obtain addition and phenyl migration in 3,3,3-triphenylpropene may be due to steric hindrance of the approach of the [IPy₂]⁺ complex. The latter was isolated as its nitrate salt and was shown to undergo a stoicheiometric and stereospecific addition to (E)-4,4-dimethylpent-2-ene to give erythro-2-iodo-1,3,3-trimethylbutyl nitrate (IIIa).