Tertiary Amines as Ligands in a Four‐Step Tandem Reaction of Hydroformylation and Hydrogenation: An Alternative Route to Industrial Diol Monomers

Abstract

With the reactions ystem [Rh(octanoate) 2 ] 2 and triethylamine, diols are produced in ah igh yields of up to 79 %w ith full conversion of intermediate aldehyde and no evidence of olefin hydrogenation. The scopeo ft he reaction was evaluated and the optimised reaction conditions were successfully scaled up to a2 Lr eactor.F inally,t he Rh/amine catalystc omplex was recycled by asimple water extraction of the diol-product.Scheme1.Industrialapproach from dcpd 1 to TCD-diol 6 vs. new route.[a] S.

Synthesis of Industrial Primary Diamines via Intermediate Diols – Combining Hydroformylation, Hydrogenation and Amination

“…According to the findings of previous investigations,, bidentate ligands only shift the formation towards aldehydes (Table , entry 1.4 & entry 1.5), meaning no active rhodium hydrogenation species is formed without an amine. These investigations showed that only rhodium and triethylamine produced high yields of TCD‐diol 6 , indicating a crucial limitation for the further application of this pathway in a tandem reaction sequence.…”

“…As reported recently by the authors, a high yield of 79 % TCD‐diol 6 was obtained in toluene and Et 3 N (entry 1.1) . If tert ‐amyl alcohol, a solvent that is widely used for direct catalytic amination reaction, was used, the activity was inhibited, leading to a TCD‐diol 6 yield of only 21 % (Table , entry 1.2).…”

“…A previous study on hydrohydroxymethylation achieved very good diol yields when tertiary amines were used as additives in an auto‐tandem reaction using rhodium catalysts . To couple both reactions, the solvent and the ligand were aligned.…”

“…TCD‐diol 6 was extracted with water, separated, isolated and purified. 1 mmol of the separated TCD‐diol 6 was then reinserted for the amination step …”

“…The compatibility of the different reaction parameters required for each individual reaction step poses a significant challenge when it comes to developing new tandem catalysis reactions. Tandem reactions such as hydroaminomethylation, hydrohydroxymethylation,, aldol condensation or epoxidation all include a hydroformylation step to obtain the intermediate aldehyde, which then undergoes further conversions to achieve the desired product. Recent investigations using a rhodium and ruthenium catalyst have combined dcpd hydroaminomethylation with the dealkylation of the resulting secondary amines with ammonia to obtain TCD‐diamine.…”