Synthesis and reactivity of alkyl-palladium N-heterocyclic carbene complexes.

The transamination of alkyl-palladium halide N-heterocyclic carbene complexes has enabled the isolation of products that reveal interesting insights into the factors which might be barriers to the development of a palladium-catalysed alkyl-amination reaction.

New synthesis of beta-sultams from pentafluorophenyl sulfonates.

A stereoselective one-pot synthesis of substituted 1,2-thiazetidine 1,1-dioxides (beta-sultams) has been achieved from heterocyclic pentafluorophenyl (PFP) sulfonates. Mild N-O bond cleavage of isoxazolidines followed by intramolecular cyclization of the amine onto the PFP demonstrates the potential utility for using the PFP sulfonate as a valuable precursor to sulfonamides. [reaction: see text].

Synthetic, structural, and mechanistic studies on the oxidative addition of aromatic chlorides to a palladium (N-heterocyclic carbene) complex: relevance to catalytic amination.

The oxidative addition products trans-[Pd(NHC)(2)(Ar)Cl] (NHC = cyclo-C[N(t)BuCH](2); Ar = Me-4-C(6)H(4), MeO-4-C(6)H(4), CO(2)Me-4-C(6)H(4)) have been isolated in good yields from the reactions of ArCl with the amination precatalyst [Pd(NHC)(2)] and structurally characterized. The former undergo reversible dissociation of one NHC ligand at elevated temperatures, and a value of 25.57 kcal mol(-1) has been determined for the Pd-NHC dissociation enthalpy in the case where Ar = Me-4-C(6)H(4). Detailed kinetic studies have established that the oxidative addition reactions proceed by a dissociative mechanism. Rate data for the oxidation addition of Me-4-C(6)H(4)Cl to [Pd(NHC)(2)] compared to that obtained for the [Pd(NHC)(2)]-catalyzed coupling of morpholine with 4-chlorotoluene are consistent with a rate-determining oxidative addition in the catalytic amination reaction. The relative rates of oxidative addition of the three aryl chlorides to [Pd(NHC)(2)] (CO(2)Me-4-C(6)H(4)Cl > Me-4-C(6)H(4)Cl > MeO-4-C(6)H(4)Cl) reflect the electronic nature of the substituents and also parallel observed trends in coupling efficiency for these aryl halides in aminations.

Studies on high-temperature amination reactions of aromatic chlorides using discrete palladium-N-heterocyclic carbene (NHC) complexes and in situ palladium/imidazolium salt protocols.

The palladium catalysed coupling of aryl chlorides and amines can be readily achieved with short reaction times when carried out at high temperatures under thermal or microwave conditions. These coupling protocols are successful using two co-ordinate palladium-N-heterocyclic carbene complexes, or imidazolium salt protocols.