Catalytic activity of Ru/tetrahydropyrimidinium salts system for transfer hydrogenation reactions

Abstract

New 1,3‐dialkyltetrahydropyrimidinium salts as NHC precursors have been synthesized and characterized. The in situ prepared three‐component 1,3‐dialkyltetrahydropyrimidinium salts/[RuCl2(p‐cymene)]2 and KOH catalyzes quantitatively the transfer hydrogenation of ketones under mild reaction conditions in 2‐propanol. Also, the molecular structure of 1,3‐bis(2‐methylbenzyl)‐3,4,5,6‐tetrahydropyrimidinium was determined using single‐crystal X‐ray diffraction. Ions of the title compound are linked by CH…Cl and OH…Cl hydrogen bonding interactions. The NCN bond angle (124.3(2)°) and CN bond lengths (1.316(3) and 1.314(3) Å) confirm the existence of strong resonance in this part of the molecule. Copyright © 2015 John Wiley & Sons, Ltd.

Ruthenium NNN complexes with a 2‐hydroxypyridylmethylene fragment for transfer hydrogenation of ketones

“…Transfer hydrogenation (TH) is an important and attractive method for reducing ketones to alcohols . Recently, Szymczak's group reported a ruthenium catalyst based on the ligand 6,6′‐dihydroxyterpyridine (dhtp) for TH of a series of ketones, reaching turnover frequencies (TOFs) up to 100 h −1 (Figure a) .…”

“…[3,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Transfer hydrogenation (TH) is an important and attractive method for reducing ketones to alcohols. [24][25][26][27][28][29] Recently, Szymczak's group reported a ruthenium catalyst based on the ligand 6,6′-dihydroxyterpyridine (dhtp) for TH of a series of ketones, reaching turnover frequencies (TOFs) up to 100 h −1 (Figure 1a). [30] In comparison with similar ruthenium complexes with 4,4′-dhtp or terpyridine, this complex shows higher catalytic efficiency.…”