New Nitrogen, Sulfur-, and Selenium-Donating Ligands Derived from Chiral Pyridine Amino Alcohols. Synthesis and Catalytic Activity in Asymmetric Allylic Alkylation

Although many chiral ligands for asymmetric catalysis have been developed, there is still a need for new structures allowing the modular approach. Recently, easy synthesis of chiral pyridine-containing beta-amino alcohols has been elaborated by opening respective epoxides with enantiomeric 1-phenylethylamine. This paper reports the synthetic transformation of beta-amino alcohols into the new complexing pyridine-containing seleno- and thioethers. The amino alcohols were effectively converted to cyclic sulfonamidates, which were reacted with thiolates or phenyl selenide nucleophile. The reaction was diastereoselective, and its outcome depended on the configuration at the substitution center. The problem was discussed considering DFT optimized structures of both diastereomeric sulfonamidates. New amino-aldimine ligands were also synthesized from chiral pyridine-containing diamines. Nine new chiral ligands were tested in the Tsuji-Trost allylic alkylation resulting in the enantiomerically enriched product in up to 75% ee. The observed stereochemical induction agrees with the prevailing nucleophilic attack at the allylic carbon laying opposite to the complexing nitrogen of pyridine in eta(3)-allylic intermediate complexes.

Automated summary

The paper describes the synthesis of new chiral ligands, including chiral pyridine-containing beta-amino alcohols synthesized by opening epoxides with enantiomeric 1-phenylethylamine, and their conversion into new complexing pyridine-containing seleno- and thioethers. The diastereoselective reaction outcomes were discussed based on DFT optimized structures of diastereomeric sulfonamidates. New amino-aldimine ligands were also synthesized and tested in Tsuji-Trost allylic alkylation, with stereochemical induction agreeing with nucleophilic attack at the allylic carbon opposite to complexing nitrogen of pyridine.