Copper(I)-Catalyzed One-Pot Sequential [3+2]/[8+2] Annulations for the (Z)-Selective Construction of Heterocyclic Diazabicyclo[5.3.0]decatrienes

Beyond 1,2,3-triazoles: Formation and Applications of Ketemines Derived from Copper Catalyzed Azide Alkyne Cycloaddition

Ketemines represent an interesting class of organic intermediates that has undergone a regrowth as a consequence of recent extensions of copper catalyzed azide alkyne cycloaddition (Cu- AAC) to other synthetic fields. This review summarizes the most recent generation methods of ketimines from CuAAC reaction, highlighting chemical properties focused on the synthesis of cyclic compounds, among others, affording a general outlook towards the development of new biologically active compounds.

Tandem CuAAC/Ring Cleavage/[4 + 2] Annulation Reaction to Synthesize Dihydrooxazines and Conversion to 2-Aminopyrimidines

A tandem CuAAC/ring cleavage/[4 + 2] annulation reaction of terminal ynones, sulfonyl azides, and oximes has been developed to synthesize functionalized dihydrooxazines under mild conditions. In particular, intermediate N-sulfonyl acylketenimines are the first example of a 4π-system participating in [4 + 2] cycloadditions, and dihydrooxazines can convert to 2-aminopyridines through ring cleavage under basic conditions.

Synthesis of N-(Isoquinolin-1-yl)sulfonamides via Ag2O-Catalyzed Tandem Reaction of ortho-Alkynylbenzaldoximes with Benchtop Stabilized Ketenimines

In this project, a moderately efficient approach to multisubstituted N-(isoquinolin-1-yl)sulfonamide derivatives was illustrated, utilizing ortho-alkynylbenzaldoximes and zwitterionic ketenimine salts in a tandem reaction catalyzed by silver oxide. The oxophilicity of Ag₂O, along with its nature as Lewis acid, pave the way for a smooth [3 + 2] cycloaddition between isoquinoline N-oxides and ketenimine species, which is a key step in this reaction. DFT calculation suggests that 1,3-dipolar cycloaddition of nitrone and ketenimine proceeds through a selective stepwise mechanism.

Gold(I)-Catalyzed [8+2]-Cycloaddition of 8-Aryl-8-azaheptafulvenes with Allenamides and Ynamides: Regioselective Synthesis of Dihydrocycloheptapyrrole Derivatives

Gold(I)-catalyzed higher-order [8+2] cycloadditions of 8-aryl-8-azaheptafulvenes 1 with allenamides 2 and ynamides 3 were studied. 1,8-Dihydrocycloheptapyrroles 4 were achieved by a regioselective [8+2] cycloaddition of azaheptafulvenes 1 and allenamides 2 in the presence of (2,4-ditBuC₆ H₃ O)₃ PAuNTf₂ as catalyst. Besides, ynamides 3 and 8-aryl-8-azaheptafulvenes 1, undergo a regioselective [8+2] cycloaddition, to give 2-amido-1,4-dihydrocycloheptapyrroles 7 in the presence of JohnPhosAuNTf₂ as catalyst. Both reactions take place with good yields and with a variety of substituents. A plausible mechanism hypothesis suggests a nucleophilic attack of the 8-azaheptafulvene to the gold activated electron rich allene or alkyne moieties of the allenamide and ynamide, respectively.

Copper(I)-Catalyzed Ketenimine Formation/Aza-Claisen Rearrangement Cascade for Stereoselective Synthesis of α-Allylic Amidines

A copper-catalyzed three-component reaction of terminal alkynes, TsN₃, and tertiary allylic amines is developed toward the one-pot synthesis of α-allylic amidines. The product was synthesized on gram scale under 1 mol % of catalyst loading. Transformations of products into alkenyl amine and other nitrogen-containing compounds are demonstrated without any loss of stereochemical information.

Inverting the reactivity of troponoid systems in enantioselective higher-order cycloaddition

The first enantioselective higher-order cycloaddition involving a tropone derivative that acts as an electron-rich 8π-component is described.

A copper-catalyzed three component reaction of aryl acetylene, sulfonyl azide and enaminone to form iminolactone via 6π electrocyclization

We developed a copper-catalyzed three component reaction of aryl acetylene, enaminone and sulfonyl azide to construct iminolactone via copper-catalyzed alkyne–azide cycloaddition (CuAAC), Michael addition of metalated ketenimine followed by elimination and 6π electrocyclization.