Formation of Allylpalladium Complexes and Asymmetric Allylation Involving Modular Bridging Diamidophosphite-Sulfides Based on 1,4-Thioether Alcohols

Abstract

A large family of P,S-bidentate diamidophosphite ligands were readily synthesized from accessible hydroxyl-thioether compounds. One type of Pd­(II) cationic allylic complex with these diamidophosphites fulfilling a P-monodentate function, and three types, where the ligands act as P,S-bridging ligands (coordination polymer and head-to-head and head-to-tail dimers), were obtained. In addition, neutral Pd­(II) halide complexes were generated in situ as common intermediates for both groups of cationic dimers. The structures of the ligands and complexes were elucidated by means of 2D-NMR and were confirmed by powder X-ray diffraction, as well as by DFT calculations. Asymmetric inducers of this type exhibited up to 94% ee in the Pd-mediated allylic substitution of (E)-1,3-diphenylallyl acetate with various C- and N-nucleophiles. Ee values of up to 80% were obtained in the Pd-catalyzed allylic alkylation of cinnamyl acetate with β-ketoesters. In addition, up to 61% ee was achieved in the asymmetric amination of 2-(diethoxyphosphoryl)-1-phenylallyl acetate with aniline. The effects of the diamidophosphite and thioether moieties on the catalytic activity and enantioselectivity were investigated.

Enantioselective [1,2]-Stevens rearrangement of thiosulfonates to construct dithio-substituted quaternary carbon centers

“… 1 Furthermore, they could also serve as useful reagents and ligands in organic synthesis. 2 Thiosulfonate is considered the line of defense against cyanide intoxication, 3 and could be used for both sulfenylation and sulfonylation. 4 For example, sulfenylation of α-sulfonyl carboxylic esters with S -methyl methanethiosulfonate resulted in dithioketals containing two sulfur substitutions with different oxidation states at the same carbon center 4 a ( Scheme 1a ).…”