Highly Selective Halide Anion-Promoted Palladium-Catalyzed Hydroformylation of Internal Alkenes to Linear Alcohols

Abstract

Here we report on our study of the palladium-catalyzed hydroformylation of alkenes. A (bcope)Pd(OTf)2 complex (bcope = bis(cyclooctyl)phosphine ethane, 2) with substoichiometrically added halide anions is a highly efficient homogeneous catalyst (precursor) to selectively convert internal linear alkenes into predominantly linear (detergent) alcohols under mild conditions. Halide anion-dependent effects on the hydroformylation reaction rate as well as its chemo- and regioselectivity are observed. Thus, the rate of hydroformylation of thermally equilibrated internal higher alkenes increases by a factor of about 6−7 with chloride/bromide and about a factor 3−4 with iodide, while the selectivity toward alcohols increases to almost 100% upon addition of a substoichiometric quantity (with respect to palladium) of the halide anion source. Curiously, the regioselectivity toward linear alcohol increases in the reverse order, i.e., iodide > bromide > chloride. From a detailed analysis of the products obtained with model substrates, it is concluded that hydrogenolysis of (bcope)palladium-acyl intermediates is strongly accelerated by the presence of halide anions. From a comparison of the catalytic performance with some related L2Pd(OTf)2 complexes, in which L2 are bidentate phosphines closely related to bcope, it also appears that the ligand plays a critical role in the promoting effect of halide anions.

Palladium‐Catalyzed Isomerization and Hydroformylation of Olefins

“…For example, by using non-coordinating anions and arylphosphine ligands primarily (oligo)ketones are produced, while increasing the ligand basicity or anion coordination strength shifted the product selectivity towards aldehydes and alcohols. [10] Herein, we report the development of new palladiumbased catalyst systems that enable the hydroformylation of different terminal and internal olefins in good selectivity and activity. Based on our previous work in hydroformylations and hydroaminomethylations with phosphine-modified rhodium catalysts, [11] we became interested in similar reactions with palladium catalysts.…”

“…[10] Hence, the testing was carried out in the presence of 0.8 mol % p-toluenesulfonic acid as cocatalyst. Unfortunately, under these conditions significant amounts of internal olefins (68 %) are produced as main products.…”

“…This observation is in accordance with the work of Drent and co-workers, who showed the superiority of DPPP in combination with trifluoroacetic acid. [10] However, the combination of [PdA C H T U N G T R E N N U N G (acac) 2 ] and several other bidentate ligands are also able to catalyze the hydroformylation of octene (Table 1, entries 1-11). Applying biaryl-type ligands such as BINAP (2,2'-bis(diphenylphosphino)-l,1'-binaphthyl) or heteroarylarylphosphines a higher selectivity towards the linear products is obtained.…”

Following palladium catalyzed methoxycarbonylation by hyperpolarized NMR spectroscopy: a parahydrogen based investigation

“…In addition, the alkoxycarbonylatyion of 1-alkynes finds a further role in the formation of unsaturated carboxylic acids that feature as building blocks in a range of situations. 3,4 Consequently, these developments illustrate just how critical early studies on the mechanism of the methoxycarbonylation of alkenes, 2,5 and more generally the palladium catalysed hydroformylation of alkenes 6,7 were for the development of an array of new clean technologies. 3 For a number of years, the parahydrogen (p-H 2 ) 8 induced polarization (PHIP) 9, 10 effect has been used to yield mechanistic insight into a range of catalytic hydrogenation and hydroformlyation reactions besides monitoring the formation of metal hydride based products.…”

Tandem Rhodium‐Catalyzed Hydroformylation–Hydrogenation of Alkenes by Employing a Cooperative Ligand System

“…Many other catalytic systems that are composed of a ligand associated with a metal, such as Co, [5] Pd, [6] Rh, [7] or Ru, [8] have been reported as potential solution to this highly relevant industrial issue. [9] However, none of these systems operates with satisfying chemoselectivity (alcohol vs. alkane; the latter resulting from competing direct reduction of the alkene) and regioselectivity (linear/branched (l/b) regioisomers resulting from unselective hydroformylation).…”