Pd‐Catalyzed Asymmetric Addition of Arylboronic Acids to Pyrazolinone Ketimines

Abstract

An asymmetric addition of arylboronic acids to pyrazolinone ketimines is reported using palladium/chiral N,N′‐disulfonyl bisimidazoline (Bim) catalytic system, producing 25 examples of enantioenriched 4‐amino‐5‐pyrazolones bearing one quaternary carbon stereocenter with 60–91% yields and 81–98% ee. The reaction demonstrates remarkable compatibility regarding pyrazolinone ketimines and arylboronic acids, rendering an enantioselective access to chiral aza‐heterocycles bearing α‐tertiary amines.

Accessing unnatural α-amino acids with tetrasubstituted stereogenic centersviacatalytic enantioselective reactions of ketimine-type α-iminoesters/α-iminoamides

“…100 b Similar chemistry involving pyrazolinone-type N -Boc ketimines 7e catalyzed by a palladium salt and chiral bis(imidazolidine) ligand 159 was also reported by the same authors (Scheme 63). 101 The authors rationalized the high enantioselectivity in this reaction through a steric repulsive interaction between the phenyl group of 159 and the functional groups on the nitrogen atom of 7c .…”

Nickel-Catalyzed, One-Pot Synthesis of Pyrazoles

“…Pyrazole moieties are widely used in bioactive molecules (Figure 1) [13] and functional materials [14][15][16][17][18]. To date, various methods for the construction of pyrazole rings are available [19][20][21][22][23][24], such as the classical Knorr pyrazole synthesis of 1,3-diketones and TsNHNH 2 , Refs [25][26][27] via direct hydrazation of propargyl alcohols A two-step synthesis and subsequent intramolecular cyclization of propargyl hydrazides, cycloaddition of [28][29][30] [3+2] terminal alkynes to hydrazones, and aldehydes/ketones generated in situ to diazo compounds [31][32][33].…”