Acceptorless and Base‐Free Dehydrogenation of Alcohols Mediated by a Dipyridylamine‐Iridium(III) Catalyst

Abstract

Several dipyridylamine-Ir(III) and dipyridylamine-Ru(II) complexes have been evaluated in the acceptorless dehydrogenation of alcohols in the absence of base additives. Iridium catalysts were found superior to ruthenium complexes and the nature of the bridging nitrogen in dipyridylamine ligands was also evidenced as a key parameter. Catalytic reactions were conducted in toluene but more sustainable solvents such as anisole and pcymene were found suitable for this transformation.

Catalytic Acceptorless Dehydrogenation (CAD) of Secondary Benzylic Alcohols into Value-Added Ketones Using Pd(II)–NHC Complexes

“…Compound 2l was prepared according to the general procedure A from its corresponding secondary alcohol (86.1 mg, 0.5 mmol, 1 eq), and the reaction mixture was purified by flash column chromatography (5% EtOAc/Hexane) to afford 2l as white solid in 88% (76.6 mg) yield. The NMR data of 2l are in accordance with the literature [64].…”

“…Compound 2l was prepared according to the general procedure A from its corresponding secondary alcohol (86.1 mg, 0.5 mmol, 1 eq), and the reaction mixture was purified by flash column chromatography (5% EtOAc/Hexane) to afford 2l as white solid in 88% (76.6 mg) yield. The NMR data of 2l are in accordance with the literature [64]. 1 H NMR (500 MHz, CDCl 3 ): δ 8.02 (dd, J = 8.2, J = 0.9 Hz, 1H), 7.68 (td, J = 7.5, J = 1.1 Hz, 1H), 7.58-7.54 (m, 1H), 7.41 (dd, J = 7.6, J = 1.3 Hz, 1H), 2.52 (s, 3H).…”

Preparation and Degradation of Rhodium and Iridium Diolefin Catalysts for the Acceptorless and Base-Free Dehydrogenation of Secondary Alcohols

“… 5 To prevent the waste generated by the base, the development of precursors operating under base-free conditions is receiving great attention. 6 They coordinate ligands, being engaged in the deprotonation step. The basic center usually resides in the first metal coordination sphere 7 and sometimes in a remote position.…”

“…The base cocatalyzes the dehydrogenation to generate an alkoxide, which binds to the metal and evolves into the carbonyl compound by β-hydrogen elimination . To prevent the waste generated by the base, the development of precursors operating under base-free conditions is receiving great attention . They coordinate ligands, being engaged in the deprotonation step.…”

Geometric Analysis and DFT Study of 2,2′-Dipyridylamine-Stabilized First-Row Transition-Metal Complexes

“…It has the ability to bind to different metal centers through variable coordination modes, which includes monodentate, bidentate, , and also as a bridging ligand . According to Brogden and Berry, dpa adopts nine possible coordination modes which makes it adaptive to different environments and has several uses in catalysis, , pharmaceutical, , photochemistry, and cancer chemotherapy. , This N -heterocyclic compound has two pyridine rings bonded to an sp 3 -hybridized amine group, as shown in Figure a.…”