Synthesis of 4-Arylidenepyrazolones by a Gold-Catalyzed Cyclization/Arylidene Group Transfer Cascade of N-Propioloyl Hydrazones

Photodecarboxylative Radical Cascade Involving N-(Acyloxy)phthalimides for the Synthesis of Pyrazolones

We disclose N'-arylidene-N-acryloyltosylhydrazides as novel skeletons for the synthesis of biologically relevant alkylated pyrazolones through a photoinduced radical cascade with N-(acyloxy)pthalimides as readily available alkyl surrogates. The reaction proceeds through the formation of a photoactivated electron donor-acceptor (EDA) complex between alkyl N-(acyloxy)phthalimide (NHPI) esters and LiI/PPh3 as a commercially available donor system. The reaction exhibits a broad scope and scalability, thereby enabling synthesis of a broad spectrum of functionally orchestrated alkylated pyrazolones under mild and transition-metal-free conditions.

Organocatalytic (5+1) benzannulation of Morita–Baylis–Hillman carbonates: synthesis of multisubstituted 4-benzylidene pyrazolones

DABCO-catalyzed (5+1) cycloaddition of MBH carbonate undergoes an α-double deprotonation pathway to de novo assemble the benzene ring.

1,2-Difunctionalizations of alkynes entailing concomitant C–C and C–N bond-forming carboamination reactions

Vicinal carboamination of alkynes is a highly reliable and efficient practical strategy for the quick preparation of valuable and diverse amine derivatives starting from simple synthons. The last decade has witnessed numerous practical methods employing transition-metal-based/metal-free carboamination approaches using alkynes for the synthesis of these N-bearing entities. Driven by the renaissance of transition metal catalysis, intermolecular and intramolecular carboamination of alkynes comprising concomitant C–N and C–C bond formation has been studied extensively. In contrast to metal catalysis, though analogous metal-free approaches have been relatively less explored in the literature, they serve as alternatives to these expensive approaches. Despite this significant progress, reviews documenting such examples are sporadic; as a result, most reports of this type remained scattered throughout the literature, thereby hampering further developments in this escalating field. In this review, different conceptual approaches will be discussed and examples from the literature will be presented. Further, the reader will get insight into the mechanisms of different transformations.

The 1,2-difunctionalization of alkynes happening through concomitant C–C and C–N bond formation strategies have provide an unified access to diversely functionalized N-bearing heterocycles.

Dissecting the Gold(I)-Catalyzed Carboaminations of N-Allyl Tetrahydro-β-carbolines to Allenes

N-Allyl tetrahydro-β-carbolines undergo gold-catalyzed cyclizations that lead to tetracyclic compounds, resulting from both ring closure and the transfer of the allylic group from the nitrogen to the carbon backbone. The final skeleton obtained depends on the nature of both the R² group of the allene and the R³ group of the allylic residue. Mechanistic studies and DFT calculations allowed the determination of all the mechanistic pathways involved in these processes, stemming from a common intermediate that evolves differently according to the substituents nature.

DFT study on the Au(i)-catalyzed cyclization of indole-allenoate: counterion and solvent effects

The base strength was revealed to be the primary factor controlling the catalytic capability of counterions. The image shows the Au(i)-catalyzed cyclization reaction of indole-allenoate to form dihydrocyclopenta[b]indole derivatives, as reported by Ma.