摘要: Hypervalent iodine reagents constitute a powerful tool in modern synthetic organic chemistry, promoting several important reactions. One such reaction is the ring contraction of cycloalkenes and cycloalkanones promoted by iodine(III) compounds, as iodobenzene diacetate, iodosylbenzene, iodotoluene difluoride, [hydroxy(tosyloxy)- iodo]benzene (Koser s reagent). This review covers all literature related to cyclic ketones olefins species.