M.J.S.M. Moreno

A novel oxidation of homoallylic alcohols under sonochemical conditions

Abstract The oxidation of 3β-hydroxy-Δ 5 -cholestenes, -pregnenes and -androstenes to the corresponding Δ4-3,6-diones has been achieved in high yields by a new one-step process, using tetra- n -propylammonium perruthenate with 4-methylmorpholine N-oxide as co-oxidant, under sonochemical conditions.

Sonochemical reduction of α, β-epoxy ketones and α′-oxygenated analogs by aluminium amalgam

Abstract The sonochemical reductive opening of α, β-epoxy ketones and their α′-oxygenated (-OH or -OAc) analogs by aluminium amalgam allows shorter reaction times, better yields of the respective β-hydroxy ketones and minimization of by-products. The rates of these reactions are affected by the intensity of the acoustic waves and by temperature.

Ultrasound assisted remote functionalization of non-activated carbon atoms: efficient in situ formation of tetrahydrofurans by sonolysis of bromohydrins with (diacetoxyiodo)benzeneI2

Abstract Ultrasonic irradiation of bromohydrins in the presence of (diacetoxyiodo)benzene and I 2 generates alkoxyl radicals which lead in situ to intramolecular hydrogen abstraction on the C-19 non-activated carbon atoms in steroids producing tetrahydrofurans selectively in very good yields. Photolysis was less effective in promoting such conversions.

Ultrasound assisted oxidations and reductions in steroid synthesis

Abstract Ultrasonic irradiation made feasible some important oxidative and reductive reactions in steroid synthesis. These unusual conditions have improved existing methods and promoted new ones. The very common 5-en-3β-ol homoallylic system in steroids was oxidized to 4-ene-3,6-diones by a new one-step process, using tetra- n -propylammonium perruthenate with a co-oxidant, under sonochemical conditions. Ultrasonic irradiation has been also successfully used to promote the generation of radicals in the hypoiodite reaction, in order to prepare tetrahydrofurans as precursors of 19-hydroxy-Δ 5 -steroids. Application of ultrasound to aluminium amalgam reductive opening of α,β-epoxy-ketones improved the reaction rates and yields of β-hydroxy ketones, in particular for α′-oxygenated counterparts. Zinc reduction of α,β-unsaturated oxosteroids has been also enhanced by ultrasound. Fast quantitative reactions led to olefins or allylic alcohols, according to the α-enone system used. Regio- and stereoselectivities are marked. A new Clemmensen-type reduction promoted on the last conditions gave a mild and effcient method to reduce selectively 3-oxo groups in polihydroxysteroids.

16α,17α‐Epoxy‐20‐oxopregn‐5‐ene‐3β,21‐diyl di­acetate

The title compound, C25H34O6, has a 3β,21-configuration, with the epoxy O atom at 16α,17α. Rings A and C have chair conformations which are slightly flattened. Because of the presence of a double bond, ring B assumes an 8β,9α-half chair conformation. Ring D has a conformation close to a 14α-envelope. Cohesion of the crystal can be attributed to van der Waals interactions and weak C—H⋯O interactions.