Hydroformylation of unsaturated compounds

Hydroformylation reaction is the addition of molecular hydrogen and carbon monoxide to an alkene, usually terminal, or 1-alkene. This is a very important reaction, which is catalyzed homogeneously in industry. Otto Roelen, a German chemist in the Ruhr chemical area, discovered the reaction in 1938. 

The mechanism of this reaction is now known with reasonable certainty. The name hydroformylation reminds us that the reaction involves addition of H and the formyl group, CHO (derived from H2 and CO) to an olefin  

The reaction enables conversion of an alkene into an aldehyde with the increase in the number of carbon atoms by one carbon atom. Generally, we can write  

The industrial importance of this reaction has been thoroughly described. 

The commonly accepted catalyst was HCo(CO)4, derived from Co2(CO)g and H2, which is formed at 150 to 180 °C, and at pressures above 200 atm. 

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Hydroformylation of unsaturated amines offer a convenient synthetic access to cyclic AT.O-hemiacetals. If performed in the presence of alcohols or orthoesters AT,O-acetals are formed. With additional N-nucleophiles N,N-acetals are obtained. These compounds are synthetically attractive building blocks and were therefore used as a key step in the synthesis of various natural products [27,35]. Thus the synthesis of (+)-prosopinine starting from enantiopure (T)-scrinc leads to a cyclic N,O-acetal functionality with the required functionality for the attachment of the side chain (Scheme 6) [36]. 

Spectacular enantioselection has been observed in hydrogenation (cf. Section 2.2) [3] and hydrometallation of unsaturated compounds (cf. Section 2.6) [4], olefin epoxidation (cf Section 2.4.3) [5] and dihydroxylation (cf Section 3.3.2) [6], hydrovinylation (cf Section 3.3.3) [7], hydroformylation (cf Section 2.1.1) [4a, 8], carbene reactions [9] (cf Section 3.1.10), olefin isomerization (cf Section 3.2.14) [10], olefin oligomerization (cf Section 2.3.1.1) [11], organometallic addition to aldehydes [12], allylic alkylation [13], Grignard coupling reactions [14], aldol-type reactions [15], Diels-Alder reactions [12a, 16], and ene reactions [17], among others. This chapter presents several selected examples of practical significance. 

Table VH. Hydroformylation of Unsaturated Halogen Compounds Table VIH. Hydroformylation of Un.saturated Nitrogen Compounds Table IX. Hydroformylation of Other Functionalized Alkenes. ...

TABLE VIL HYDROFORMYLATION OF UNSATURATED HALOGEN COMPOUNDS (Continued)... 

TABLE VIII. HYDROFORMYLATION OF UNSATURATED NITROGEN COMPOUNDS... 

Even though the hydroformylation of alkenes is an important reaction for the functionalization of unsaturated compounds with enormous potential, the above mentioned examples already show the limitations of using molecularly enlarged catalysts in combination with membrane filtration the hydroformylation reaction is typically performed at elevated temperature (40-80 °C) as well as under a syngas... 

Macromolecular metal complexes of soluble dendrimers with catalytically active groups on their surface have been used in hydrogenation [112, 113], Kharasch addition [114], Heck reactions and hydroformylation [115-118], metathesis of unsaturated compounds [119-121], oxidation [122], etc. The use of dendrimers in most cases enabled catalyst reuse and also influenced the activity and selectivity of the processes. 

With Unsaturated Compounds. The reaction of unsaturated organic compounds with carbon monoxide and molecules containing an active hydrogen atom leads to a variety of interesting organic products. The hydroformylation reaction is the most important member of this class of reactions. When the hydroformylation reaction of ethylene takes place in an aqueous medium, diethyl ketone [96-22-0] is obtained as the principal product instead of propionaldehyde [123-38-6] (59). Ethylene, carbon monoxide, and water also yield propionic acid [79-09-4] under mild conditions (448—468 K and 3—7 MPa or 30—70 atm) using cobalt or rhodium catalysts containing bromide or iodide (60,61). 

In a similar manner, polymers with unsaturated chains or side chains can be converted to polyamines [66-69]. Conjugated diolefins usually undergo hydroformylation with low selectivities [70]. Mostly hydrogenation of at least one double bond occurs and mixtures of various saturated and unsaturated amines and diamines are obtained [71]. Similar to alkenes also alkynes may serve as unsaturated compounds in hydro aminomethylation reaction sequences. Although synthetically attractive, only a few investigations towards hydroformylation and hydroaminomethylation of alkynes in the presence of N-nuclcophilcs are known. Usually a preferred transformation to furanonic derivatives is observed under hydroformylation conditions [27]. 

In conclusion, the applicability of the transition metal catalyzed hydroformylation of easily accessible functionalized or non-functionalized unsaturated compounds is expanded by its implementation in reaction sequences, tandem reactions or domino reactions. The hydroformylation can be combined with simple functional group transformations, such as reduction or isomerization, or with C,0-, C,N- and, most importantly, C,C-bond forming reactions. It can be expected that more interesting examples and applications will be presented in the future. 

Bohnen et report a hydroformylation method to convert olefins or olefinically unsaturated compounds in the presence of at least one rhodium compound and sulfonated arylphosphines in ILs based on a quaternary ammonium ion or the equivalent of a multiply charged ammonium ion and organic sulfonates or sulfates. 

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