Copper-Catalyzed Annulation/A3 -Coupling Cascade: Diastereodivergent Synthesis of Sterically Hindered Monocyclic Oxazolidines Bearing Multiple Stereocenters

Synthesis of Oxazolidines and Dihydroxazines via Cyclization of α-Aminated Ketones

A new approach to oxazolidines and dihydroxazines was developed by regioselective cyclization of α-aminated ketones under transition metal-free conditions. Oxazolidine derivatives were generated in the presence of chloro benziodoxole and TFA, while dihydroxazines were formed without a hypervalent iodine reagent. The reaction was performed under room temperature and gave the products in good to excellent yields.

Metal-Catalysed A3 Coupling Methodologies: Classification and Visualisation

The multicomponent reaction of aldehydes, amines, and alkynes, known as A3 coupling, yields propargylamines, a valuable organic scaffold, and has received significant interest and attention in the last years. In order to fully realise the potential of the metal-based catalytic protocols that facilitate this transformation, we summarise substrates, in situ and well-characterised synthetic methods that provide this scaffold and attempt a monumental classification considering several variables (Metal, Coordinating atom(s), Ligand type and name, in-situ or well-characterised, co-catalyst, catalyst and ligand Loading (mol%), solvent, volume, atmosphere, temperature, microwave, time, yield, selectivity (e.e. d.r.), substrate name, functionality, loading (amines, aldehydes, alkynes), and use of molecular sieves). This pioneering work creates a valuable database that contains 2376 entries and allows us to produce graphs and better visualise their impact on the reaction.

Microwave-Assisted Cu(I)-Catalyzed Synthesis of Unsymmetrical 1,4-Diamino-2-butynes via Cross-A3-Coupling/Decarboxylative A3-Coupling

1,4-Diamino-2-butynes display both chemical and physiological properties. Here a highly efficient synthesis avenue to generate unsymmetric 1,4-diamino-2-butynes has been developed by microwave-assisted Cu(I)-catalyzed cross-A³-coupling/decarboxylative coupling of two different amines, formaldehyde, and propiolic acid through a domino process. This multicomponent reaction provides a series of target products in moderate to good yields with high chemoselectivity.

Microwave-Assisted Palladium-Catalyzed Reductive Cyclization/Ring-Opening/Aromatization Cascade of Oxazolidines to Isoquinolines

An efficient palladium-catalyzed reaction of N-propargyl oxazolidines for the construction of 4-substituted isoquinolines under microwave irradiation is developed. This transformation proceeds through a sequential palladium-catalyzed reductive cyclization/ring-opening/aromatization cascade via C-O and C-N bond cleavages of the oxazolidine ring. The practical value of this method has also been explored by conducting a millimole-scale reaction, as well as by transforming the isoquinoline into a key intermediate for the synthesis of a lamellarin analogue.