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

Abstract

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.

A green synthesis of highly substituted 1,5-diketones

“…This procedure was carried out at rt. All the 30 literature procedures required that the reaction media be heated above 50 o C. [21][22][23][24] Therefore our procedure is more energyefficient.…”

“…The reaction times ranged from 1-17 h and the yields from 95-84%. 30 Typical 300 mg-scale synthesis procedure using the synthesis of 4a as an example…”

Economical and efficient aqueous reductions of high melting-point imines and nitroarenes to amines: promotion effects of granular PTFE

“…This is different from our previous observation in the hydrolysis of steroidal epoxides. 48 One possible reason for this is that the differences in solubilities were not large enough and other factors dominated. However, the reaction rates of some of the reactions that produced liquid products (2a, 2f, 2g, 2m) (Table 1, entries 1, 6, 7, 13) were faster than those that produced solid products (2e, 2h, 2j, 2k, 2l) (Table 1, entries 5, 8, 10-12).…”

Aqueous Reduction of Iodosteroids to Deoxysteroids

“…Although other VSSHMP substrates have been used in reactions mediated by water, they are often bis-or triphasic and metal reagents have not been used as the solid phase. 20,21,29,30 In this aqueous system, water and Aliquat 336 may facilitate the electron transfer from the solid zinc to the iodosteroid. Therefore, the aqueous reduction is faster and higher yielding than reductions mediated by organic solvents.…”

“…In previous research, we have carried out a series of aqueous organic reactions of VSSHMP compounds in the presence of granular PTFE and a catalytic amount of Aliquat 336. 20,21 We now report a methodology for the conversion of iodosteroids to deoxysteroids mediated by water in the presence of granular PTFE and a catalytic amount of Aliquat 336.…”