Quantitative 'On Water' Ring-Opening of Steroidal Epoxides Accelerated by Sand: A Green Procedure

摘要

Dihydroxylated steroids have been prepared quantitatively by stirring a mixture of a very sparingly soluble high-melting-point (VSSHMP) steroidal epoxide, polytetrafluoroethylene (PTFE) sand, and aqueous H2SO4; no organic solvents or phase transfer catalysts were used. The sand and aqueous H2SO4 are highly recyclable. The promoting effects of the sand for these "on water" reactions have been demonstrated for the first time. This is a green, waste-free, mild, and operationally simple procedure. Various functional groups such as ketones, esters, ethers, ketals, epoxides on D-rings, and α,β-unsaturated ketones all survived these reaction conditions. This methodology is useful for using less organic solvents, reducing the cost of the products and protecting the environment.