Copper(II)-Mediated Intramolecular Cyclopropanation of Ketene N,X-Acetals (X = S, O, N) under Mild Conditions

Metal-Free Electrocatalytic Synthesis of Fused Azabicycles from N-Allyl Enamine Carboxylates

An electrocatalytic approach to access structurally significant azabicyclic scaffolds from N-allyl enamine carboxylates is illustrated. This metal-free method functions exclusively with a catalytic amount of iodide, strategically employed to electrochemically generate a reactive hypervalent iodine species, which facilitates the cascade bicyclization processes with enhanced precision and efficiency. Excellent functional group compatibility was observed, enabling the synthesis of a series of azabicycle derivatives. Detailed mechanistic and electrochemical studies enhance the comprehension of the reaction sequence.

Synthesis of 3-Azabicyclo[3.1.0]hexane Derivates

3-Azabicyclo[3.1.0]hexanes are an important class of nitrogen-containing heterocycles that have been found to be key structural features in a wide range of biologically active natural products, drugs, and agrochemicals. As a cutting-edge area, the synthesis of these derivatives has made spectacular progress in recent decades, with various transition-metal-catalyzed and transition-metal-free catalytic systems being developed. In this review, we provide an overview of recent advances in the efficient methods for the synthesis of 3-azabicyclo[3.1.0]hexane derivatives since 2010, emphasizing the scope of substrates and synthesis' applications, as well as the mechanisms of these reactions.

AgNTf2 catalyzed cycloaddition of N-acyliminium ions with alkynes for the synthesis of the 3,4-dihydro-1,3-oxazin-2-one skeleton

A catalyzed process for the synthesis of the 4,6-substituted 3,4-dihydro-1,3-oxazin-2-one skeleton has been developed through cycloaddition of in situ generated acyliminium intermediates with alkynes. A range of chain N,O-acetals and terminal alkynes were amenable for this mild transformation. As a result, a series of desired cycloaddition products were obtained in moderate to good yields.

I2-Promoted [4 + 2] cycloaddition of in situ generated azoalkenes with enaminones: facile and efficient synthesis of 1,4-dihydropyridazines and pyridazines

A facile and efficient strategy for the synthesis of 1,4-dihydropyridazines and pyridazines through I2-promoted [4 + 2] cycloaddition of in situ generated azoalkenes with enaminones has been developed. The switch in selectivity is attributed to the judicious choice of different reaction temperatures. The key features of this work include controllable and selective synthesis, good functional group tolerance, good to excellent reaction yields, metal/base-free conditions, and also applicability to one-pot methodology.