Regioselectivity Switch in Palladium‐Catalyzed Allenylic Cycloadditions of Allenic Esters: [4+1] or [4+3] Cycloaddition/Cross‐Coupling

Abstract

The first Pd-catalyzed asymmetric allenylic [4+ +1] cycloaddition was successfully developed. Alternatively,tuning the Pd catalyst switched the reactivity toward an unprecedented [4+ +3] cycloaddition/cross-coupling. Ligands play av ital role in controlling the reaction pathway,a llowing highly selective access to different products from identical substrates.B iological evaluation of the obtained compounds led to the discovery of new antitumor targets.Apossible mechanism is proposed, suggesting two interesting catalytic cycles for the cycloaddition with palladium-butadienyls.T his study also demonstrated the potential and utility of allenic esters as 1,4-biselectrophiles and C 4 synthons for participating in cycloaddition reactions.

Direct access to spirocycles by Pd/WingPhos-catalyzed enantioselective cycloaddition of 1,3-enynes

“…In addition, effective chiral catalyst systems that are applicable to the establishment of asymmetric addition of enols/enolates to unsaturated hydrocarbons are comparatively limited. As our continuous interest in asymmetric cycloadditions [40][41][42][43][44][45][46] , we explored the possibility of transition-metal hydride-based cycloaddition strategy for the direct catalytic asymmetric spirocycle synthesis.…”

Palladium-Catalyzed [2+3] Cycloaddition/Cross-Coupling Reaction: Z/E and Diastereoselective Synthesis of Dendralene-Functionalized Dihydrofurans

“…On the basis of the results in Scheme , related reports, − and our previous work, we proposed a possible reaction mechanism (Scheme ). The oxidative addition of 1a by the Pd 0 catalyst provides Pd II butadienyl intermediate I , which then experiences allenylic substitution with 2a to give species II , which tautomerizes to III .…”

“…However, cycloaddition with palladium-butadienyl intermediates remains elusive. Recently, Shao’s group reported Pd-catalyzed selective [4+3] or [4+1] cycloaddition/cross-coupling reactions via altered ligands for the construction of biologically active spiro and fused ring compounds using the palladium-butadiene species in allenyl acetates as C4 synthons (Scheme b) …”

“…Recently, Shao's group reported Pd-catalyzed selective [4+3] or [4+1] cycloaddition/cross-coupling reactions via altered ligands for the construction of biologically active spiro and fused ring compounds using the palladium-butadiene species in allenyl acetates as C4 synthons (Scheme 1b). 4 To expand on our previous work on cycloaddition reactions, 5 we herein describe the cycloaddition/crosscoupling of 3-oxo-nitriles with palladium-butadienyl intermediates (Scheme 1c). This reaction uses type B terminal allenylic compounds as C2 synthons and 1,2-biselectrophiles in the cycloaddition reactions.…”

Catalytic Asymmetric and Divergent Synthesis of Tricyclic and Tetracyclic Spirooxindoles: Controllable Site-Selective Electrophilic Halocyclization of 1,6-Enynes

“…7 Reaction strategies allowing site-divergence represent one of the most cutting-edge developments in organic synthesis. As our continued interest in the asymmetric construction of spirooxindoles, 8 and divergent reaction development, 9 we herein report a new method combining these two tools for the catalytic asymmetric and divergent synthesis of spirooxindoles. Specifically, a modular, efficient, and stereoselective assembly of tricyclic and tetracyclic 3,3′pyrrolidonyl spirooxindoles from a common set of starting materials was developed via a one-pot chiral Brønsted base catalyzed asymmetric propargylation for the synthesis of oxindole 1,6-enynes and a subsequent site-divergent and highly diastereoselective electrophilic iodocyclization of 1,6enynes (Scheme 1).…”