Photooxygenation of 2-propargylfurans: a path to structurally diverse nitrogen-containing 5-membered rings.

The photooxygenation of 2-propargylfurans enabled access to original nitrogen-containing cyclopentenones and related compounds in a one-pot fashion. By employing readily-available substrates such as furans and amines, we succeeded in achieving a high degree of molecular complexity. Relying on the introduction of an alkyne moiety and tailored substrates, this transformation reveals a new facet for reaction sequences featuring the photooxygenation of furans.

Synthesis of Cyclopenta[ b]piperazinones via an Azaoxyallyl Cation.

A new and efficient reaction sequence between 2-furylcarbinols, anilines, and α-haloamides has been developed to afford highly functionalized cyclopenta[ b]piperazinones. This transformation was accomplished through an aza-Piancatelli cyclization/azaoxyallyl cation trapping with a complete control of the diastereoselectivity.

Harnessing the Lewis Acidity of HFIP through its Cooperation with a Calcium(II) Salt: Application to the Aza-Piancatelli Reaction.

A method to extend the scope of the aza-Piancatelli reaction between 2-furylcarbinols and anilines is depicted. We found that 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) is the solvent of choice for this transformation, as it outcompetes the usual solvents in terms of rate and yield. Side reactions and other issues raised by the title reaction are prevented, thereby providing an avenue to complex molecules that were previously inaccessible. Lewis acidity studies and computations were carried out to unveil the role of HFIP. Based on these results, we propose that HFIP is, in fact, acting as a Lewis acid and that its acidity can be enhanced when combined with a calcium(II) salt.