Branched-Selective Hydroformylation of Nonactivated Olefins Using an N-Triphos/Rh Catalyst

Abstract

We report a catalytic system comprised of nitrogen-centered di-or triphosphine ligands in conjunction with rhodium that is capable of delivering branched aldehydes from terminal olefin substrates which commonly give more linear aldehydes than branched. The incorporation of an apical nitrogen atom into the ligand backbone dramatically improves the reaction rate. Mechanistic and labelling studies suggest the unusual selectivity is due to the irreversible trapping of the Rh-alkyl species along the branched pathway, in comparison to the more reversible linear pathway. A pre-catalytic equilibrium mixture of rhodium species was observed by high-pressure in situ NMR spectroscopy, suggesting this equilibrium is the catalytic resting state.

Phosphorus coordinated Rh single-atom sites on nanodiamond as highly regioselective catalyst for hydroformylation of olefins

“…It is well known that hydroformylation of terminal aliphatic alkenes usually gave linear aldehydes in high regioselectivity ( b/l < 0.1), and the branched-selective hydroformylation of terminal aliphatic alkenes was highly challenging. The most recent work was reported by Nozaki and co-workers 53 . With the specifically designed nitrogen-centered triphosphine ligand, the corresponding Rh complex catalysts (1.0 mol% Rh) gave a b/l ratio of 1.1 with completed conversion in the hydroformylation of 1-hexene at 100 °C, 3.5 h, and 2.0 MPa.…”

Palladium‐Catalyzed Hydroformylation of Alkenes and Alkynes

“…While hydroformylation reactions have been extensively studied and broadly applied in academia and industry for almost a century, many challenges remain unsolved. In particular, noteworthy are (i) regioselectivity issues, including branchedselectivity for terminal alkyl alkenes, [81][82][83][84][85][86][87][88][89][90] β-selectivity for (hetero)aryl alkenes [91][92][93][94] , or any site-selectivity for unsymmetrical internal alkenes and alkynes, [73,[95][96][97][98][99] (ii) chemoselectivity issues, including hydrogenation side-processes in reactions of alkynes or isomerization processes of internal alkyl alkenes, as well as (iii) activity issues in reactions of terminal alkynes, all of which proved to be difficult to address comprehensively with the most common Rh-and Co-catalysis. On the other hand, the catalytic capacity of complexes of other metals was established many years ago, [30,42] but they remained understudied with few reports appearing sporadically.…”

Tandem hydroformylation/isomerization/hydrogenation of bio-derived 1-arylbutadienes for the regioselective synthesis of branched aldehydes

“…[5] More recently, by the employment of specially designed ligands, this regioselectivity was surpassed. [6][7][8][9][10][11][12][13] When the terminal C=C bond has an electron-withdrawing group, a phenyl ring or a conjugated C=C in the alpha position, the tendency to form branched products is higher. In this context, the hydroformylation of conjugated dienes opens opportunities for the synthesis of branched products, provided the selectivity can be controlled.…”