Cyclometalated palladium pre-catalyst for N-alkylation of amines using alcohols and regioselective alkylation of sulfanilamide using aryl alcohols

Abstract

Simple pyrazole based palladacycle-phosphine with a high turnover has been developed and applied for the N-alkylation of amines and sulfanilamide using alcohols as substrates by hydrogen borrowing strategy. N-alkylation of primary and secondary amines resulted in high isolated yields at 100–130 °C, under solvent free conditions. More challenging secondary aliphatic as well as aromatic alcohols were also successfully utilized as alkylating agents under similar reaction conditions. The turn over number reached up to 43000 for N-benzylation of aniline using benzyl alcohol. Notably, regioselective N-alkylation of 2-aminobenzothiazole and 4-aminobenzenesulfonamide to the corresponding 2-N-(alkylamino)azoles and 4-amino-(N-alkyl)benzenesulfonamides using alcohols as alkylating agents have been achieved using our new pre-catalyst-phosphine system.