Chelation‐Driven Rearrangement of Primary Alkyl Aminopalladation Products to Stable Trisubstituted Alkyl–Palladium Complexes

Abstract

The formation of highly substituted carbon centers using catalysis has been a widely sought after goal, but complexes of highly substituted carbon atoms with transition metals are rare, and the factors that affect the relative stability of complexes with differentially substituted carbon atoms are poorly understood. In this study, a set of equilibrating alkyl-palladium complexes were subtly tuned to form either a primary or trisubstituted alkyl complex as the more thermodynamically favored state, depending on either the substrate or reaction conditions. An X-ray crystal structure of the trisubstituted alkyl-palladium complex is presented and compared with the corresponding primary alkyl complex. The mechanism for rearrangement and the factors that drive the change in stability are discussed.

Ligand-Controlled Regioselective Pd-Catalyzed Diamination of Alkenes

“…In 2005, Muñiz described a palladium-catalyzed intramolecular diamination reaction of alkenes for the synthesis of cyclic ureas (Scheme a, top) . Michael has reported Pd­(II)-catalyzed diamination of alkenes using N -fluorobenzenesulfonimide (NFSI) as an electrophilic aminating reagent (Scheme a, bottom) . These reactions exclusively undergo 5- exo aminopalladation of alkenes to afford the functionalized pyrrolidines, due to the coordination effect between protecting group on nitrogen and palladium .…”

Transition‐Metal‐Catalyzed 1,2‐Diaminations of Olefins: Synthetic Methodologies and Mechanistic Studies

“…Inspired by 5-exo aminopalladation, [190][191][192][193] asymmetric 6endo aminoacetoxylation and mechanistically analogous amino-fluorination, aminonitroxylation, aminofluorometh-oxylation reactions of alkenes, [194][195][196][197][198][199][200] Guosheng Liu and coworkers recently unveiled strategically attractive and operationally simple pyridinyloxazoline (Pyox) ligand controlled regioselective Pd(OAc) 2 (10 mol %)-catalyzed vicinal diamination of protected-amino tethered unactivated alkenes 98 (Scheme 24). [201] This approach offered access to diverse variety of amino-functionalized piperidines p via 5-exo-diamination (15 examples, yield = 58-87 %).…”