Synthesis of Imidazolinium Salts by Pd/C‐Catalyzed Dehydrogenation of Imidazolidines

Abstract

A method for the synthesis of imidazolinium salts through a catalytic dehydrogenation was developed using Pd/C as a catalyst with ammonium salt as an additive. Optimization of the reaction conditions revealed the existence of a proton source that was necessary to accomplish the reaction. Under the optimal conditions, oxidation‐sensitive components, such as an allyl, a furan, and a thiophene can be introduced into the corresponding imidazolinium salts. In addition to the varied N‐substituents, the presented method can be used to synthesize a series of 2‐substituted imidazolinium salts.

Synthesis of a N‐heterocyclic Olefin‐Ligated Pd Complex [(NHO)Pd{[2‐(CH3O)C6H4]3P}Cl2] as a Catalyst for Suzuki−Miyaura Coupling

“…[26] The somewhat unstable free cis-diamine was promptly treated with a ketone in the presence of NaBH 3 CN to afford N,N'-dialkylated cis-diamine as a crude mixture, which was subsequently cyclized using acetaldehyde to form N,N'-dialkylated 2-methylimidazolidines 2 a-2 d. [27] The 2-methylimidazolidines 2 a, 2 b, and 2 d were then dehydrogenated using Pd/C as a catalyst (Method A) to accomplish the syntheses of NHO precursors 3 a, 3 b, and 3 d in good yields (60 to 73 % for 3 steps). [28] In the case of 2 c, the dehydration did not work properly, which we presumed to be a case of steric hindrance, and oxidation with NCS and a subsequent counter anion exchange with the use of NH 4 BF 4 (Method B) was conducted to afford NHO precursor 3 c in a 64 % yield in 3 steps.…”

Extent of carbon nitride photocharging controls energetics of hydrogen transfer in photochemical cascade processes

“…3). This compound is formed from 2c and acetaldehyde, which was generated in situ upon triethylamine oxidation 35 . The imine derived from vaniline and 4-trifluoromethylbenzyl amine did not give the corresponding coupling product, likely due to interaction of a phenolic proton with g-CN surface and the subsequent ES-PCET 36,37 rather than tertiary amine.…”