Regio-and Stereoselective Ring Opening of Epoxides with Sodium Phenylselenide under Phase Transfer Conditions

Abstract

The ring opening reaction of a wide range of mono-, di-and trisubstituted epoxides with the phenylselenide anion under PTC conditions provides a simple, mild and efficient method for preparation of b-hydroxy phenylselenides with high regio-and stereoselectivity in yields from 67 to 98%. The reactions are carried out in aqueous NaOH/ THF using aminoiminomethanesulfinic acid (thiourea dioxide, TDO) to generate sodium phenylselenide from diphenyldiselenide.

Diastereoselective and Scalable Synthesis of 6-(S)-Hydroxycannabidivarin

“…Diastereoselective reduction of readily available S -(+)-carvone 17 by employing sodium borohydride and ceric chloride furnished cis -carveol 18 in high yield and purity (97:3 dr ) (Scheme ). , The reported diastereoselective epoxidation using m -CPBA was adapted from the literature to afford cis -epoxide 16 in high yield and diastereoselectivity (>98:2 dr ) which was subsequently reacted with sodium phenylselenide. , In this step, treatment of diphenyldiselenide with sodium borohydride generates a nucleophilic sodium phenylselenide species which attacks epoxide 16 regio- and diastereoselectively to afford 19 in high yield. Intermediate 19 was then treated with benzoyl chloride in the presence of DMAP to yield 15 which was ultimately treated with hydrogen peroxide and 2-methyl-buten-2-ol to give the desired tertiary allylic alcohol 14 . , We found that adding the aqueous solution of hydrogen peroxide slowly at 55 °C allowed for the one-pot selenoxide formation and elimination.…”

“…The first step would consist of the epoxide ring opening of 16 using diphenyl diselenide followed by benzoylation to give 15 . Subsequent oxidation of the phenylselenide 15 followed by elimination of the corresponding selenoxide would afford 14 . Proceeding via elimination of the selenoxide intermediate was preferred over the alternative amine oxide or sulfoxide due to the mild elimination conditions.…”

“…Subsequent oxidation of the phenylselenide 15 followed by elimination of the correspond-ing selenoxide would afford 14. 23 Proceeding via elimination of the selenoxide intermediate was preferred over the alternative amine oxide or sulfoxide due to the mild elimination conditions. In addition, the synthesis of 16 is well-referenced and can be achieved from S-(+)-carvone 17 in a regio-and diastereoselective fashion in two steps�reduction of the ketone via Luche reduction followed by epoxide formation.…”

“…25,26 The reported diastereoselective epoxidation using m-CPBA was adapted from the literature to afford cisepoxide 16 in high yield and diastereoselectivity (>98:2 dr) which was subsequently reacted with sodium phenylselenide. 23,24 In this step, treatment of diphenyldiselenide with sodium borohydride generates a nucleophilic sodium phenylselenide species which attacks epoxide 16 regio-and diastereoselectively to afford 19 in high yield. Intermediate 19 was then treated with benzoyl chloride in the presence of DMAP to yield 15 which was ultimately treated with hydrogen peroxide and 2-methyl-buten-2-ol to give the desired tertiary Scheme 3.…”