Catalyst-Free Conjugate Addition of Thioacids to Activated Olefins Accelerated in Water

Abstract

Michael addition of thioacetic and thiobenzoic acids to activated olefins was investigated in the presence of water under catalyst-free conditions. This process, in addition to being green, has an excellent yield. With simple filtration, high-quality products were obtained on a large scale. Competitive dithiane formation and ester cleavage were not observed. Also, excellent yield was obtained using this simple process for the final step of spironolactone synthesis.

Keywords:

• Activated olefins
• Michael addition
• thioacid
• water

ACKNOWLEDGMENTS

Many thanks to the Faculty of Chemistry of Tarbiat Moallem University for supporting this work.

Notes

^a Isolated yield.

^b Reaction conditions: chalcone (5 mmol), thioacid (5.5 mmol), and water (10 mL).

^a Isolated yield.

^b Reaction conditions: activated olefin (5 mmol), thioacid (5.5 mmol), and water (10 mL).

^c Reported yield by Li et al.^[10b] is shown in parentheses.

^d 40% of thiol was obtained.

^e 20% of thiol was obtained.

^f No diastereoselectivity was observed.