Synthesis of 9‐Substituted‐1,8‐Dioxooctahydroxanthenes by an Efficient Iodine‐Catalyzed Cyclization

New 1,8-dioxooctahydroxanthenes with substituents in the 2-, 3-, and 9-positions were obtained by cyclization with iodine from tandem Michael/Michael adducts. The X-ray molecular structure of the methyl 2-(1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)acetate (3a) was solved and shows the parallel laminae packing of these molecules. Furthermore, we reported the structure of intermediate 4 isolated from this reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)