Switchable palladium-catalyst reaction of bromomethyl sulfoxides, CO, and N-nucleophiles: aminocarbonylation at Csp3 versus oxidative carbonylation of amines.

The palladium-catalyzed reaction of α-bromomethyl sulfoxides, carbon monoxide, and N-nucleophiles follows different reaction pathways according to the catalytic system and the reaction conditions. The Pd-xantphos catalyst affords high yields of α-sulfinyl amides by an aminocarbonylation process and is the first example of this type of transformation for a nonbenzylic sp(3)-hybridized carbon. On the other hand, the oxidative carbonylation of amines occurs with α-bromomethyl sulfoxides, carbon monoxide, and catalytic Pd(PPh(3))(4) under aerobic conditions, yielding ureas and oxalamides from either primary or secondary amines. The reaction with ambident nucleophiles such as amino alcohols was highly selective and took place exclusively at the amino group despite the presence of the alcohol functionality. In parallel to the reaction paths for simple amines, amino alcohols were converted into hydroxy sulfinyl amides when the reaction was catalyzed by Pd-xantphos, while Pd(PPh(3))(4) catalyst afforded cyclic carbamates. The alkoxycarbonylation reaction of bromomethyl sulfoxides with simple alcohols and CO leading to the corresponding sulfinyl esters is also described.

Competitive and selective Csp3-Br versus Csp2-Br bond activation in palladium-catalysed Suzuki cross-coupling: an experimental and theoretical study of the role of phosphine ligands.

Phosphine ligands have been demonstrated to have an effect on reactivity and selectivity in the competitive intramolecular palladium-catalysed Suzuki-Miyaura coupling of dibromo sulfoxide 1a possessing two different hybridised electrophilic carbons. It was found that the bromine bond to the sp(3)-hybridised carbon is selectively replaced in the presence of unhindered phosphines such as PPh(3) or xantphos. The use of hindered phosphine ligands such as P(o-tol)(3) and P(1-naphthyl)(3) reversed the selectivity, conducting the cross-coupling at the Csp(2)-Br. Identical trends were observed in external competition experiments carried out with bromomethyl sulfoxide and different substituted bromoarenes. DFT and DFT/MM calculations showed that the selectivity observed is mainly due to the different facility of the ligands to dissociate. Bisphosphine catalysts favour coupling at the sp(3) carbon, whereas monophosphine catalysts prefer the sp(2) carbon.

First synthesis of beta-keto sulfoxides by a palladium-catalyzed carbonylative Suzuki reaction.

[reaction: see text] An unprecedented palladium-catalyzed three-component cross-coupling reaction between alpha-bromo sulfoxide, carbon monoxide, and aromatic boronic acids provides a new and efficient approach to the synthesis of beta-ketosulfoxides. The reaction takes place under mild conditions with a wide range of variously substituted aryl and heteroaryl boronic acids. The carbonylative cross-coupling reaction is strongly favored over competing direct cross-coupling and homocoupling processes, except with boronic acids carrying strong electron-withdrawing substituents.