MARCH 1967 ADDITION OF IODINE ISOCYANATE TO OLEFINS 541 but does give an INCO adduct when treated with a preformed solution of iodine isocyanate. The presence of silver salts does not seem to influence the reaction, so that filtration of the silver salt is unnecessary either in the in situ or the preformed INCO reaction. The INCO addition to olefins proceeds by formation of a threemembered ring iodonium ion intermediates and ...