Electronic vs. Steric Effects in the Addition of Iodine Isocyanate to Olefins1

The reaction of INCO with a number of olefins has been studied with a view toward elucidating electronic and steric influences in the addition. The stereospecific addition of INCO to cis- and trans-2-butene and β-deuteriostyrene is consistent with the intermediacy of a three-membered iodonium ion. A definite dependency on steric factors is evidenced by the I-t-Bu regiospecificity in the INCO addition to t-butylethylene. The structure proof in these systems was facilitated by our finding that hydrogenolysis of the iodo function in iodo carbamates is possible. Except in diaxial iodo carbamates for which zinc treatment leads to olefin by elimination, this method serves for the introduction of a carbamate function starting with olefins. Although no methyl migration or neighboring hydroxyl participation was observed during INCO addition, examples of skeleton rearrangement have been found.