Ultrasound-promoted preparation of disteryl ethers catalyzed by montmorillonite K 10

In the presence of montmorillonite K 10, 5(6)-unsaturated sterols (1) were heated under ultrasound at 45°C in dichloromethane for 2–5.5 h to provide 3β,3′β-5(6)/5′(6′)-unsaturated disteryl ethers (2) in 35–79% yield. Meanwhile, 3α,3′α-diandrost-5-en-17-one-3-yl ether (3a) and 3α,3′α-dipregn-5-en-20-one-3-yl ether (3b) were also obtained as by-products from 3β-hydroxyl-androst-5-en-17-one (1a) and 3β-hydroxyl-pregnan-5-en-20-one (1b) respectively.