http://aether.cmi.ua.ac.be/artikels/MB_09616.pdf

Tandem catalysis: a taxonomy and illustrative review

The condensation of formaldehyde with p-alkylphenols under alkaline conditions, a reaction dating back to the days of Baeyer and Zinke, affords initially linear polyphenols, which, once a certain temperature is achieved, yield cyclic oligomeric phenolic compounds (Scheme 1). One-step, multigram synthetic procedures have now been developed, which by varying either the temperature or amount of base used in the preparation, readily afford the tetrameric, hexameric, and octameric phenolic ring systems, bridged by methylene (-CH2-) spacers. Ring systems with up to 20 phenolic residues are now known, although methods of preparation for these higher members, and for those with an odd number of phenolic residues, are usually low yielding. The smaller members of the family adopt a cone-shaped structure, hence the name calix[n]arene coined by Gutsche, from the Greek “calix” meaning vase, where n denotes the number of phenolic residues. Such a bowl shape results in the formation of a hydrophobic, electron-rich cavity, which is well-suited to the formation of inclusion complexes, particularly cations.5 The synthetic methodology has also been adapted to allow for the incorporation of bridging groups other than methylene, such as dimethyleneoxa (-CH2OCH2-), thia (-S-), and aza [-CH2N(R)CH2-] bridged calixarenes,6 and these additional donors can provide extra binding sites.

The use of calixarenes in metal-based catalysis.

Carbon monoxide was discovered and identified in the 18th century. Since the first applications in industry 80 years ago, academic and industrial laboratories have broadly explored CO's use in chemical reactions. Today organic chemists routinely employ CO in organic chemistry to synthesize all kinds of carbonyl compounds. Despite all these achievements and a century of carbonylation catalysis, many important research questions and challenges remain. Notably, apart from academic developments, industry applies carbonylation reactions with CO on bulk scale. In fact, today the largest applications of homogeneous catalysis (regarding scale) are carbonylation reactions, especially hydroformylations. In addition, the vast majority of acetic acid is produced via carbonylation of methanol (Monsanto or Cativa process). The carbonylation of olefins/alkynes with nucleophiles, such as alcohols and amines, represent another important type of such reactions. In this Account, we discuss our work on various carbonylations of unsaturated compounds and related reactions. Rhodium-catalyzed isomerization and hydroformylation reactions of internal olefins provide straightforward access to higher value aldehydes. Catalytic hydroaminomethylations offer an ideal way to synthesize substituted amines and even heterocycles directly. More recently, our group has also developed so-called alternative metal catalysts based on iridium, ruthenium, and iron. What about the future of carbonylation reactions? CO is already one of the most versatile C1 building blocks for organic synthesis and is widely used in industry. However, because of CO's high toxicity and gaseous nature, organic chemists are often reluctant to apply carbonylations more frequently. In addition, new regulations have recently made the transportation of carbon monoxide more difficult. Hence, researchers will need to develop and more frequently use practical and benign CO-generating reagents. Apart from formates, alcohols, and metal carbonyls, carbon dioxide also offers interesting options. Industrial chemists seek easy to prepare catalysts and patent-free ligands/complexes. In addition, non-noble metal complexes will interest both academic and industrial researchers. The novel Lucite process for methyl methacrylate is an important example of an improved catalyst. This reaction makes use of a specific palladium/bisphosphine catalyst, which led to the successful implementation of the technology. More active and productive catalysts for related carbonylations of less reactive olefins would allow for other large scale applications of this methodology. From an academic point of view, researchers continue to look for selective reactions with more functionalized olefins. Finally, because of the volatility of simple metal carbonyl complexes, carbonylation reactions today remain a domain of homogeneous catalysis. The invention of more stable and recyclable heterogeneous catalysts or metal-free carbonylations (radical carbonylations) will be difficult, but could offer interesting challenges for young chemists.

Transition-metal-catalyzed carbonylation reactions of olefins and alkynes: a personal account.

Coordination chemistry of calix[4]arene derivatives with lower rim functionalisation and their applications

The metal-catalyzed isomerization–hydroformylation tandem reaction is of great importance for the production of linear aldehydes starting from internal olefins, but also, the shift of the double bond from a terminal position into the interior of an alkyl chain and the subsequent hydroformylation can be of interest. This review aims to summarize problems and achievements in this area under particular consideration of results published by the Leibniz-Institut fur Katalyse (LIKAT) in the past two decades. A main focus is given to the variation of metals (Co, Rh, Ru, Pd, Pt, Fe) and phosphorus ligands used for the tandem reaction.

Isomerization–Hydroformylation Tandem Reactions

New Phosphorus Ligands for the Rhodium‐Catalyzed Isomerization/Hydroformylation of Internal Octenes

New calix[4]arene-based bis-phosphonites, bis-phosphites and bis-O-acylphosphites were synthesized and characterized. Treatment of these P-ligands with selected rhodium and platinum precursors led to mononuclear complexes that were satisfactorily characterized. The solid state structure of the dirhodium(I) complex 14 has been determined by X-ray diffraction. The two rhodium centres are bridged by two chloro ligands; one rhodium atom is further coordinated by calix[4]arene phosphorus atoms and the other by cyclooctadiene. The new calix[4]arene P-ligands were tested in the Rh(I) catalyzed hydroformylation of 1-octene. All Rh(I) complexes catalyzed the reaction leading to high chemoselectivity with regard to the formation of aldehydes. Yields and n/iso-selectivities depended on the reaction conditions. Average yields of 80 % and n/iso-ratios of about 1.3 to 1.5 were observed. High yields of aldehydes can be achieved using the methoxy substituted P-ligands at low Rh:ligand ratios.



Auf Calix[4]arenen basierende Bis-phosphonite, Bis-phosphite und Bis-O-acyl-phosphite als Liganden in der rhodium(I)-katalysierten Hydroformylierung von 1-Octen



Neue auf Calix[4]arenen basierende Bis-phosphonite, Bis-phosphite und Bis-O-acyl-phosphite wurden synthetisiert und charakterisiert. Die Umsetzung dieser Phosphorliganden mit ausgewahlten Rhodium- und Platinvorstufen fuhrte zu mononuklearen Komplexen, die vollstandig charakterisiert wurden. Durch eine Rontgenstrukturanalyse konnte die Struktur des Dirhodium( I)-Komplexes 14 im festen Zustand bestimmt werden. Die beiden Rhodiumzentren sind durch zwei Chlorliganden verbruckt, wobei das eine Rhodiumatom an die Phosphoratome des Calix[4]-arens und das andere Rhodiumatom durch das Cyclooctadien koordiniert ist. Die neuartigen phosphorhaltigen Calix[4]aren-Liganden wurden in der Rhodium(I)-katalysierten Hydroformylierung von 1-Octen getestet. Alle Rh(I)-Komplexe katalysierten die Reaktion bei hoher Chemoselektivitat, bezogen auf die Bildung von Aldehyden. Ausbeuten und n/iso-Selektivitaten waren dabei von den Reaktionsbedingungen abhangig. Durchschnittliche Ausbeuten von 80 % und n/iso-Verhaltnisse von 1.3 bis 1.5 wurden beobachtet. Hohe Ausbeuten an Aldehyden bei geringen Rhodium:Ligand-Verhaltnissen konnten durch den Einsatz von methoxysubstituierten Phosphorliganden erzielt werden.

Calix[4]arene‐based Bis‐phosphonites, Bis‐phosphites, and Bis‐O‐acyl‐phosphites as Ligands in the Rhodium(I)‐catalyzed Hydroformylation of 1‐Octene

A bisphosphite of the formula I wherein R1, R2, R3 and R4 are each hydrogen, an aliphatic, alicyclic, aliphatic-alicyclic, aromatic, aromatic—aromatic, aliphatic-aromatic hydrocarbon or heterocyclic or aliphatic-heterocyclic group having from 1 to 50 carbon atoms, F, Cl, Br, I, —CF3, —OR7, —COR7, —CO2R7, —CO2M, —SR7, —SO2R7, —SOR7, —SO3R7, —SO3M, —CO2NR7R8, NR7R8, N═CR7R8, NH2, where R1 to R4 are identical or different and may be covalently linked to one another; R7 and R8 are each hydrogen, a substituted or unsubstituted, aliphatic or aromatic hydrocarbon radical having from 1 to 25 carbon atoms, and may be identical or different; M is an alkali metal, alkaline earth metal, ammonium or phosphonium ion; Q is a substituted or unsubstituted divalent aliphatic, alicyclic, aliphatic-alicyclic, aromatic, aliphatic-aromatic hydrocarbon, heterocyclic or aliphatic-heterocyclic radical having from 1 to 50 carbon atoms where HO-Q-OH is a diol; W and X are each a substituted or unsubstituted aliphatic, alicyclic, aliphatic-alicyclic, aromatic, aromatic—aromatic, aliphatic-aromatic hydrocarbon, heterocyclic or aliphatic-heterocyclic radical having from 1 to 50 carbon atoms which may be identical or different or covalently linked to one another, provided that when the phosphite oxygens linked to W and X are each linked to an aromatic ring, then they are linked to different aromatic rings, metal complexes thereof, and a method for the hydroformylation of olefins.

Novel bisphosphite compounds and their metal complexes

The synthesis of calix[4]arene-based phosphorus diamides and phosphites is described. These oligocyclic ligands have been tested in the Rh(I)- catalyzed hydroformylation of 1-octene. Depending on the reaction conditions, yields up to 99% and n/iso-selectivities between 0.7 and 2.6 have been observed. tert-Butyl groups on the upper rim of the calix[4]arene template had a beneficial effect on the catalytic reaction. In general biuret-derived P-ligands were superior. For comparison, the corresponding “monomeric” ligands have also been synthesized and were employed in the catalytic reaction. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:577–585, 2001

Synthesis of new calix[4]arene‐based phosphorus ligands and their application in the Rh(I) catalyzed hydroformylation of 1‐octene

Phosphites of the formula I or II 
and their metal complexes, their preparation and the use of the phosphites as ligands in catalytic reactions, in particular in processes for the hydroformylation of olefins, are described.

Christine Kunze

Papers

New Phosphorus Ligands for the Rhodium‐Catalyzed Isomerization/Hydroformylation of Internal Octenes

Calix[4]arene‐based Bis‐phosphonites, Bis‐phosphites, and Bis‐O‐acyl‐phosphites as Ligands in the Rhodium(I)‐catalyzed Hydroformylation of 1‐Octene

Novel bisphosphite compounds and their metal complexes

Synthesis of new calix[4]arene‐based phosphorus ligands and their application in the Rh(I) catalyzed hydroformylation of 1‐octene

Phosphite compounds and the metal complexes thereof