Chemical building blocks are obtained from microalgae biomass via an integrated extraction/catalytic upgrading approach.

Via an all-catalytic route, long-chain diamines were prepared by the catalytic direct amination of long-chain diols, derived from plant oils. High conversion was achieved with good selectivity, with the amount of nitrile impurities formed suppressed to a low level. From the lignocellulose-based 5-hydroxymethylfurfural (5-HMF), or from bis(hydroxymethyl)furan, 2,5-bis(aminomethyl)furan (BAMF) was generated. 5-HMF was converted in a one-pot, one-step direct amination and reductive amination using ammonia. In both cases, the reaction proceeded very efficiently. In the combined amination and reductive amination, the H-2 concentration is a rate-limiting factor. Reducing the partial pressure of H-2 also shortened the reaction time required significantly. Polycondensation of the long-chain diamines with long-chain diacids led to higher molecular weight polyamides, illustrating the quality of the diamines obtained by this synthetic approach as monomers.

In this chapter, the role of water in metal pincer–catalyzed reactions is summarized. Briefly three categories can be described: (1) Water can act as polar and protic solvent for biphasic catalysis, with water-soluble pincer complexes in the catalyst phase. (2) The use of water in aqueous phase alcohol and aldehyde-reforming processes for low-temperature hydrogen generation. (3) The use of water in aqueous phase oxidation reactions where water acts as oxygen source, for example, for the oxidation of alcohols to carboxylic acids or the oxidation of amines to amides. Thus, water plays a role for potentially recyclable catalyst systems toward more sustainable organic synthesis or low-temperature energy storage and conversion systems.

A two-step one-pot synthesis of benzene from the five-fold unsaturated fatty acid eicosapentaenoic acid (EPA), a component of microalgae oils, is presented. By a sequence of olefin metathesis and the catalytic dehydrogenation of the resulting 1,4-cyclohexadiene, two equivalents of benzene are effectively formed per EPA substrate molecule. As the only major by-products, 5-octenoic acid and 5-decenedioic acid are formed. Performing the dehydrogenation step under hydrogen pressure results in the formation of their saturated analogues, sebacic acid and octanoic acid, both desirable products, while the simultaneous dehydrogenation step to benzene is not hampered.

A direct catalytic upgrading on as-cultivated microalgae biomass is demonstrated. Via CO-free alkoxycarbonylation of the contained lipids with the use of formates, diesters were produced in high conversion and selectivity from monounsaturated fatty acids from Phaeodactylum tricornutum microalgae. Via this procedure, extraction and functionalization occur in one step, circumventing the need for separate workup procedures of the biomass. The products are valuable building blocks for renewable polyester materials.

The catalytic activity of a series of Ru-PNP pincer ligand complexes was studied in the direct amination of alcohols with ammonia. It turned out that all complexes of PNP ligands bearing a secondary amine showed no activity in this hydrogen-shuttling reaction sequence, while all complexes of homologous ligands bearing a tertiary amine gave active catalysts. Further comparative studies on catalysts bearing an acridine-based PNP pincer ligand and a PNP ligand of the Xantphos family provided valuable mechanistic insight that led to the design of a highly active catalyst. It appears that in the group of ligands studied here only ligands that do not form stable Ru-amido complexes are active alcohol amination catalysts.

Microalgae oil serves as a feedstock for a biorefinery approach to mid-chain (di-)carboxylic acid esters, currently only accessible via demanding synthetic routes. Via the butenolysis of mono- and poly-unsaturated fatty acids, short-chain unsaturated fatty acid methyl esters and mono- and di-enes were produced in a high selectivity. These olefins were further processed into value added linear mid-chain (di-)carboxylic acid esters via isomerizing alkoxycarbonylation. Model compounds such as eicosapentaenoic acid were used to study the reactions including the screening of metathesis catalysts and to identify all formed products. Notably, eicosapentaenoic acid, a five-fold unsaturated fatty acid relatively abundant in algae, is successfully converted to four equivalents of heptadiene, which was carbonylated to the linear diester (dimethyl azelate). The butenolysis and subsequent isomerizing alkoxycarbonylation were performed on the algae oil extracted from the diatom Phaeodactylum tricornutum. Despite the multicomponent mixture of numerous lipids and non-lipid compounds present in algae oil, high conversion and high selectivity for the desired products were achieved in both reactions. This approach provides access to several carboxylic mono- and di-acid esters of chain length ranging from C6 to C12 (amongst others azelaic acid ester, suberic acid ester and dodecanedioic acid ester), that are in demand but to which access is limited currently, fully based on algae oils as a renewable resource.

A Ru-based half sandwich complex used in amine and alcohol racemization reactions was found to be active in the splitting of secondary amines to primary amines using NH3. Conversions up to 80% along with very high selectivities were achieved. However, after about 80% conversion the catalyst lost activity. Similar to Shvo's catalyst, the complex might deactivate under the influence of ammonia. It was revealed that not NH3 but mainly the primary amine is responsible for the deactivation.

By employing an amination catalyst, previously used in the direct synthesis of amines from alcohol with ammonia, n-amino-alcohols could be selectively cyclized to either the amide or the amine. By the addition of water, the amine could be produced as the major product whereas adding a sacrificial ketone as a hydrogen acceptor resulted in the amide as the major product. Without an additive a mixture of both the amine and the amide was observed. N-substituted amino-alcohols solely gave cyclic amines under these conditions. From 2-(n-alkanol) anilines the cyclic amines were produced, where the n-propanol derivative selectively formed quinoline as the major product.

The Ru-catalyzed direct amination of alcohols with ammonia was investigated for the RuHCl(CO)(PPh3)(3)/Xantphos system in order to gain mechanistic insight. For several Ru(II) precursor complexes the influence of different additives on catalytic performance was investigated. NMR studies revealed that the reaction of RuHCl(CO)(PPh3)(3)/Xantphos with the alcohol in the presence of a strong base initially formed an inactive dihydrido Ru species. However, by addition of a ketone, the dihydride was (re)activated, where the corresponding imine is the actual activator, formed by immediate condensation of the ketone with ammonia In the absence of a base, added ketone significantly enhanced catalyst activity. Catalytically inactive RuCl2(PPh3)(3) could be activated by base, demonstrating that also complexes without the CO ligand give active catalysts. On the basis of these observations a mechanism was proposed, closely related to known transfer hydrogenation mechanisms.

With RuHCl(CO)(PPh3)3 as the starting material, the complexes RuHCl(CO)(PPh3)(L) were prepared for L = Xantphos and closely related ligands. Their catalytic activity in the direct amination of cyclohexanol showed large differences depending on the different backbone structures. In those complexes the Xantphos-type ligand backbones are slightly bent and display fluxionality, studied by VT-NMR. This was assigned to the “flipping” of the backbone via the bridging atoms in the xanthene backbone. Via line shape analysis of the peaks, the Gibbs free energy of activation of the flipping movement was found to be around 56 kJ/mol in all cases. However, the activation enthalpy and entropy differed considerably. Employing RuCl2(PPh3)3 as the precursor resulted in the trans-coordinated complexes RuCl2(PPh3)(L) for L = Xantphos, Sixantphos. Fluxionality was no longer observed, due to the fact that in these complexes the O atom in the backbone also coordinates to the Ru.

A slightly adapted catalyst system has been successfully applied in the direct amination of primary and secondary alcohols. Moreover, the applicability to diols has been shown, giving high selectivity towards the primary diamines. It was found that the Ru/P ratio as well as the amount of ammonia used are highly important in this system, especially for higher substrate loadings. The catalyst was employed on a larger batch scale for the conversion of isomannide to the corresponding diamine. Additionally, it was shown that the catalyst is stable for at least six consecutive runs. No significant loss of activity and selectivity was observed.

Hydrogen shuttle: For the first time secondary alcohols and ammonia can be directly converted into primary amines with a selectivity of up to 99?% by using a simple ruthenium/phosphine catalyst (see scheme; R1, R2= alkyl, aryl, alkenyl; M=[Ru3(CO)12]; and L=phosphine ligand).

Angewandte ChemieVolume 122, Issue 44 p. 8307-8310 Zuschrift Direkte Aminierung von sekundären Alkoholen mit Ammoniak† Dennis Pingen, Dennis Pingen Schuit Institute of Catalysis, Laboratory of Homogeneous Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Niederlande), Fax: (+31) 40-245-5054 www.catalysis.nl/homogeneous_catalysisSearch for more papers by this authorDr. Christian Müller, Dr. Christian Müller Schuit Institute of Catalysis, Laboratory of Homogeneous Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Niederlande), Fax: (+31) 40-245-5054 www.catalysis.nl/homogeneous_catalysisSearch for more papers by this authorProf. Dr. Dieter Vogt, Prof. Dr. Dieter Vogt [email protected] Schuit Institute of Catalysis, Laboratory of Homogeneous Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Niederlande), Fax: (+31) 40-245-5054 www.catalysis.nl/homogeneous_catalysisSearch for more papers by this author Dennis Pingen, Dennis Pingen Schuit Institute of Catalysis, Laboratory of Homogeneous Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Niederlande), Fax: (+31) 40-245-5054 www.catalysis.nl/homogeneous_catalysisSearch for more papers by this authorDr. Christian Müller, Dr. Christian Müller Schuit Institute of Catalysis, Laboratory of Homogeneous Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Niederlande), Fax: (+31) 40-245-5054 www.catalysis.nl/homogeneous_catalysisSearch for more papers by this authorProf. Dr. Dieter Vogt, Prof. Dr. Dieter Vogt [email protected] Schuit Institute of Catalysis, Laboratory of Homogeneous Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Niederlande), Fax: (+31) 40-245-5054 www.catalysis.nl/homogeneous_catalysisSearch for more papers by this author First published: 29 July 2010 https://doi.org/10.1002/ange.201002583Citations: 74 † Wir danken T. Staring für technische Unterstützung und A. Skowron für die deutsche Übersetzung. Diese Arbeit wurde im Rahmen des CatchBio-Programms finanziert vom Netherlands Ministry of Economic Affairs und dem Netherlands Ministry of Education, Culture, and Sciences. C.M. dankt der Netherlands Organization for Scientific Research (NWO-CW) für Finanzierung. Read the full textAboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract Wasserstoff-„Shuttling“ vom Alkohol auf einen Katalysator und von dort auf das Imin ermöglichte die erste direkte Umsetzung sekundärer Alkohole mit Ammoniak zu primären Aminen. Unter Verwendung einfacher Ruthenium-Phosphan-Katalysatoren wurden Ausbeuten bis 99 % erzielt. R1, R2 = Alkyl, Aryl, Alkenyl; M=[Ru3(CO)12]; L=Phosphanligand. Supporting Information Detailed facts of importance to specialist readers are published as ”Supporting Information”. 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