Photoinduced Transformations. 77. A Four-Step Substitution of a Carbonyl Group of Steroidal Ketones by an Oxygen Atom. A New Method for the Synthesis of Cyclic Ethers

Article abstract of DOI:10.1021/jo00214a016

We set out to describe a new and versatile method for transforming steroidal five- and six-memered cyclic ketones as a starting materials into steroidal cyclic ethers with the same ring size via four steps; Baeyer-Villiger oxidation of steroidal ketone to a lactone followed by its reduction with DIBAL gives the corresponding lactol.The irradiation of the hypoiodite generated in situ by means of the reaction of the lactol by an excess of mercury(II)oxide-iodine and pyridine in benzene gives formates arising from a regiospecific β-scission of th C-C bond.These formates can read ily be transformed into oxasteroids by treatment with a complex metal hydride or methyllithium.By this new method a variety of steroidal cyclic ketones were transformed into the corresponding cyclic ethers in a good overall yields.The stereochemical integrity of the chiral center adjacent to the carbonyl group of the starting cyclic ketones is maintained throughout this transformation.