Palladium(0)-Catalyzed Allylic Aminations: Kinetics and Mechanism of the Reaction of Secondary Amines with Cationic [(η3-allyl)PdL2]+ Complexes

Synthesis of chiral branched allylamines through dual photoredox/nickel catalysis

Allylamines are versatile building blocks in the synthesis of various naturally occurring products and pharmaceuticals. In contrast to terminal allylamines, the methods of synthesis of their branched congeners with internal, stereodefined double bonds are less explored. This work describes a new approach for the preparation of allylamines via cross-coupling of alkyl bromides with simple 3-bromoallylamines by merging the photoredox approach and Ni catalysis. The reaction proceeds under mild conditions, under blue light irradiation, and in the presence of an organic dye, 4CzIPN, as a photocatalyst. The scope of suitable reaction partners is broad, including alkyl bromides bearing reactive functionalities (e.g., esters, nitriles, aldehydes, ketones, epoxides) and N-protected allylamines, as well as N-allylated secondary and tertiary amines and heterocycles. The employment of non-racemic starting materials allows for rapid and easy construction of complex multifunctional allylamine derivatives without the loss of enantiomeric purity.

Total Synthesis of (-)-Nodulisporic Acids D, C, and B: Evolution of a Unified Synthetic Strategy

A unified synthetic strategy leading to the total synthesis of (-)-nodulisporic acids D, C, and B is described. Key synthetic transformations include a nickel-chromium-mediated cyclization, an aromatic ring functionalization employing a novel copper-promoted alkylation, a palladium-catalyzed cross-coupling cascade/indole ring construction, and a palladium-mediated regio- and diastereoselective allylic substitution/cyclization reaction, the latter to construct ring D.

Palladium-catalyzed enantioselective allylic alkylation of trifluoromethyl group substituted racemic and acyclic unsymmetrical 1,3-disubstituted allylic esters with malonate anions

We accomplished the enantioselective allylic alkylation of racemic and acyclic unsymmetrical 1,3-disubstituted allylic esters with a malonate anion by DYKAT.

A DFT investigation into the origin of regioselectivity in palladium-catalyzed allylic amination

The addition of amines or aziridines to prenylacetate is catalyzed by palladium phosphine complexes. The first-formed products have recently been shown to be the branched olefins R2NCMe2CH=CH2, R = alkyl, or R2 = 1,2-C6H10, for example. DFT calculations using the MPW1K functional were performed on reactions of the suspected intermediate η3-prenyl complex [Pd(η3-Me2CCHCH2)(PH3)2]+ with dimethylamine and ethylene imine. The activation barrier for the nucleophilic attack by the amine or the aziridine is calculated to be similar for either the sterically hindered site of the π-allyl ligand to produce the branched olefin complex or the unhindered site to give the linear olefin complex. Therefore, these calculations do not reveal the experimentally observed preference for attack. This observation, along with the experimental observation of lack of isomerization of the branched olefin product of the aziridine reactions, appears to rule out the intermediacy of a π-allyl complex [Pd(η3-Me2CCHCH2)L2]+, L = phosphine or L2 = diphosphine in the C–N bond-forming reaction.Key words: allyl palladium, amine, aziridine, DFT, mechanism, catalysis.

Oxidative diamination of alkenes with ureas as nitrogen sources: mechanistic pathways in the presence of a high oxidation state palladium catalyst

A first palladium-catalyzed intramolecular diamination of unfunctionalized terminal alkenes has recently been reported. This study investigates the details of its mechanistic course based on NMR titration, kinetic measurements competition experiments, and deuterium labeling. It concludes a two-step procedure consisting of syn-aminopalladation with an unligated palladium(II) catalyst state followed by oxidation to palladium(IV) and subsequent C-N bond formation to give the final products as cyclic diamines. Related reactions employing sulfamides give rise to aminoalkoxy-functionalization of alkenes. This process was investigated employing deuterated alkenes and found to follow an identical mechanism where stereochemistry is concerned. It exemplifies the importance of cationic palladium(IV) intermediates prior to the final reductive elimination from palladium and proves that the nucelophile for this step stems from the immediate coordination sphere of the palladium(IV) precursor. These results have important implications for the general development of alkene 1,2-difunctionalization and for the individual processes of aminopalladation and palladium-catalyzed C(alkyl)-N bond formation.