A new [3+2] cycloaddition strategy for the direct synthesis of highly substituted pyrroles from the readily available α‐acylketene dithioacetals (or related substrates) and commercially available propargylamines under mild metal‐free conditions has been developed. In this reaction, the acyl group plays a critical role in driving the conjugate addition of propargylamine and further cyclization to give pyrroles. Furthermore, the wide scope was confirmed by the preparation of 1,2,3,4‐tetrasubstituted pyrroles (60–70% yields) via a formal 1,2‐acyl migrating [3+2] cycloaddition pathway with N‐methylprop‐2‐yn‐1‐amine as the secondary amine component.

A new strategy for the highly efficient one-pot synthesis of 3-amino-/alkylthio-cyclobut-2-en-1-ones based on the cyclization of acyl ketene dithioacetals is disclosed. In addition, the rearrangement of 3-amino-cyclobut-2-en-1-ones to 4-quinolone derivatives is described.

No abstract

3 + 2] Cycloadditions of α-Acyl Ketene Dithioacetals with Propargylamines: Pyrrole Synthesis in Water. -Various polysubstituted pyrroles are synthesized in a single step. The reaction of secondary amine (VIII) shows a different behavior in the presence or absence of base. -(REN, C.-Q.; DI, C.-H.; ZHAO*, Y.-L.; ZHANG, J.-P.; Tetrahedron Lett. 54 (2013) 11, 1478-1481, http://dx.

3 + 2] Cycloaddition of Propargylamines and α-Acylketene Dithioacetals: A Synthetic Strategy for Highly Substituted Pyrroles. -The synthesis of highly functionalized pyrroles via a new cycloaddition strategy is presented. In this reaction, readily available starting materials react with propargylamines under mild transition metal-free conditions. The acyl group plays a critical role in driving the conjugate addition of propargylamine and further cyclization to give pyrroles. -(ZHAO*, Y.-L.; DI, C.-H.; LIU, S.-D.; MENG, J.; LIU, Q.; Adv. Synth. Catal. 354 (2012) 18, 3545-3550, http://dx.