Micellar Catalysis for Sustainable Hydroformylation

Abstract

It is here reported a fully sustainable and generally applicable protocol for the regioselective hydroformylation of terminal alkenes, using cheap commercially available catalysts and ligands, in mild reaction conditions (70 °C, 9 bar, 40 min). The process can take advantages from both micellar catalysis and microwave irradiation to obtain the linear aldehydes as the major or sole regioisomers in good to high yields. The substrate scope is largely explored as well as the application of hydroformylation in tandem with intramolecular hemiacetalization thus demonstrating the compatibility with a broad variety of functional groups. The reaction is efficient even in large scale and the catalyst and micellar water phase can be reused at least 5 times without any impact in reaction yields. The efficiency and sustainability of this protocol is strictly related to the in situ transformation of the aldehyde into the corresponding Bertagnini's salt that precipitates in the reaction mixture avoiding organic solvent mediated purification steps to obtain the final aldehydes as pure compounds.

Switching Mechanistic Pathways by Micellar Catalysis: A Highly Selective Rhodium Catalyst for the Hydroaminomethylation of Olefins with Anilines in Water

“…In our previous work on the HF under micellar catalysis conditions, we found that the addition of NaHSO 3 to the reaction mixture plays a key role for obtaining linear aldehydes in excellent yields, preventing a subsequent aldol condensation typically occurring in HFs in aqueous media …”

“…More recently, Zhang developed an intriguing protocol on the same substrates performing the reaction in water as the sole solvent; tailor-made water-soluble ligands were necessary (Scheme 1 entry 4). 45 As we have obtained very good results in performing HF in water by using micellar catalysis, 46 we were intrigued about the possibility of developing a micellar catalyzed HAM protocol in water using commercially available inexpensive catalysts and ligands. Commonly known as micellar catalysis, the effect of micellar media on chemical transformations is known since the 1970s, 47−49 and has been recently refreshed by Lipshutz and coworkers 33,50,51 and several groups 52−54 finding noteworthy industrial applications.…”

“…As we have obtained very good results in performing HF in water by using micellar catalysis, we were intrigued about the possibility of developing a micellar catalyzed HAM protocol in water using commercially available inexpensive catalysts and ligands. Commonly known as micellar catalysis, the effect of micellar media on chemical transformations is known since the 1970s, − and has been recently refreshed by Lipshutz and coworkers ,, and several groups − finding noteworthy industrial applications. ,− Thereby the role of the surfactants is decisive in micellar catalysis conditions .…”

Linear Selective Hydroformylation of 2‐Arylpropenes Using Water‐Soluble Rh‐PNP Complex: Straightforward Access to 3‐Aryl‐Butyraldehydes

“…The hydroformylation reactions were conducted in toluene‐H 2 O (v/v=1 : 1) biphasic system, and sodium dodecylbenzene sulfonate (SDBS, 0.86 mol %) was added, serving as the surfactant. The use of surfactant was reported to promote micellar catalysis in hydroformylation, [22a,26] and micelle formation was observed in the mixture before the reaction (Figure S5). This biphasic system allowed the facile separation of the organic product phase from the aqueous catalyst phase.…”

An Intramolecular Hydroaminomethylation-Based Approach to Pyrrolizidine Alkaloids under Microwave-Assisted Heating

“…Although characterized by high atom economy, HF and HAM are featured by harsh reaction conditions in terms of temperature (>100 °C), syngas pressure (50 bar) and time (24 h) [ 26 , 27 , 28 , 29 , 30 ]. However, many reactions that require very harsh conditions, such as aminocarbonylation, hydrogen borrowing, reductive amination, HF, and HAM itself, can benefit from MW assistance [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. We report here a generally relevant, mild, and sustainable method for the synthesis of pyrrolizidine nuclei via an intramolecular HAM process under MW dielectric heating.…”