Copper(II)-Catalyzed [3+2] Annulation of Thioamides with AIBN: Facile Access to Highly Functionalized Thiazolidin-4-ones
Pragya Pali
,
Dhananjay Yadav
,
Gaurav Shukla
,
Maya Shankar Singh∗
We gratefully acknowledge financial support in the form of fellowships (to P.P., D.Y. and G.S.) from the Science and Engineering Research Board (SERB), New Delhi (CRG/2019/000058) and the University Grants Commission (UGC), Institutes of Eminence (IoE) Incentive Grant (Scheme No. 6031). We are also grateful for funding from the Council of Scientific and Industrial Research, New Delhi [02(0348)/19/EMR-II] and for a JC Bose National Fellowship, New Delhi (JCB/2020/000023).
An efficient and versatile copper-catalyzed intermolecular radical [3+2] annulation of thioamides with azobisisobutyronitrile (AIBN) is described. This two-component copper(II)-catalyzed transformation is achieved in one pot via cascade formation of C–S/C–N bonds through cyclization of an in situ generated N,S-acetal intermediate derived from a β-ketothioamide. This operationally simple method allows direct access to synthetically demanding thiazolidin-4-ones in good to excellent yields containing diverse functional groups of different electronic and steric nature. The readily available reaction partners, the avoidance of expensive/toxic reagents and a gram-scale synthesis are additional attributes of this strategy. AIBN plays a dual role as a radical initiator and an unusual source of a two-carbon coupling partner. Notably, the products possess Z stereochemistry with regard to the exocyclic C=C double bond at position 2 of the thiazolidine ring.
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7a Prices for AIBN ($40 kg–1) are from https://www.energychemical.com/front/index.htm (accessed December, 2021)
7b For detailed information on AIBN see:
Simpkins N. S.
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