The preparation of enantiomerically pure compounds is one of the major areas of organic chemistry. Much emphasis is placed on the elaboration of naturally occurring starting materials and on the development of techniques for enantio-selective transformations of achiral substrates. In this field, chiral aziridines form an attractive class of compounds, since they are available in enantiomerically pure (or highly enriched) form by a variety of procedures and can be used for asymmetric synthesis in a number of different ways. The chemistry of aziridines is dominated by ring-opening reactions, the driving force for which is relief of ring strain. By suitable choice of sub-stituents on the carbon and nitrogen atoms, excellent stereo- and regiocontrol can be attained in ring-opening reactions with a wide variety of nucleophiles, including organometallic reagents; this makes chiral aziridines useful as substrates for the synthesis of important biologically active species including alkaloids, amino acids, and /Mactam antibiotics. Substrate-controlled diastereo-selective synthesis is also possible by use of aziridines as removable chiral auxiliaries, while metalation at a ring carbon atom allows aziridines to be used as chiral reagents for asymmetric synthesis. Chiral bisaziridines can act as ligands for transition metals, and applications in the challenging field of enantioselective catalysis can be envisioned. Today, the exclusion of three-membered carbo- and heterocycles from the arsenal of the organic chemist is inconceivable.

Chiral Aziridines—Their Synthesis and Use in Stereoselective Transformations

The main contributions in the field of first-row transition-metal-catalyzed (base-metal-catalyzed) carbonylative transformations have been summarized and discussed. The contents have been divided according to the electrophiles applied, followed by the different types of nucleophiles. Their reaction mechanisms and applications have been emphatically discussed.

First-Row Transition-Metal-Catalyzed Carbonylative Transformations of Carbon Electrophiles.

Transition-metal catalysed C–N bond activation has attracted much attention and become one of the most promising bond disconnection and formation strategies that encompass a broad spectrum of applications in many reactions. In this tutorial review, efficient strategies for catalytic cleavage of C(sp)–N, C(sp2)–N and C(sp3)–N bonds and their applications in new C–C and C–N bond formation reactions are summarized.

/pdf/transition-metal-catalysed-c-n-bond-activation-1r8ryjv4of.pdf

Transition-metal catalysed C–N bond activation

Publisher Summary This chapter discusses the roles played by certain nucleophile adducts of metal–coordinated carbon monoxide in the stoichiometric and catalytic chemistry of metal–carbonyl complexes and relatively recent developments for systems where oxygen or nitrogen bases have been used as the nucleophiles. The syntheses, spectral characterizations, and chemical reaction studies of various nucleophile–carbonyl complexes are described with the goal of drawing attention to how such adduct formation not only activates the carbonyl directly involved for further reaction but also influences the reactivities of the balance of the complex. Preparation by direct addition of a nucleophile anion Nu – to a coordinated CO has been a widely applicable approach. Nuclear magnetic resonance (especially 13 C NMR) and infrared spectroscopy have proved the most used and successful diagnostic tools in characterizing the formation and transformations of various L n M–(CO)Nu complexes and related species. Reactions of uncharged nucleophiles with coordinated CO provide a different situation. Kinetics studies of systems for which characterizable nucleophilecarbonyl adducts have been isolated are relatively few.

Nucleophilic Activation of Carbon Monoxide: Applications to Homogeneous Catalysis by Metal Carbonyls of the Water Gas Shift and Related Reactions

Transition Metal Mediated Carbonylative Ring Expansion of Heterocyclic Compounds

Anhand metallorganischer Modellreaktionen wurde die Cyclocarbonylierung von Vinyloxiranen zu ungesattigten δ-Lactonen untersucht. Die photochemisch initiierte Komplexierung von Vinyloxiranen 1 (X = O) an Fe(CO)5 verlauft mehrstufig und fuhrt zu diastereomeren cis- bzw. trans-Ferralactonen 2. Vertreter beider Verbindungstypen (2k, 2 k′) wurden kristallographisch charakterisiert und chemisch bezuglich ihres Verhaltens gegenuber Nucleophilen und Elektrophilen studiert. Mit primaren Aminen bilden sich Ferralactame 7 unter Wanderung des Allylsystems sowie unter Konfigurationsumkehr an C-1 und C-4, was den exo-Angriff des Amins an C-4 des Allylsystems beweist. Bei Einwirkung von HO⊝ hingegen zerfallen Ferralactone zu CO⊝ und Dien-komplexen 10, wobei lediglich an C-1 eine Konfigurationsumkehr beobachtet wird. In diesem Fall greift HO⊝ somit an einer terminalen Carbonylgruppe an. Elektrophile bewirken die Spaltung der CO-O-Bindung unter Bildung von Allyl-Kationen (14, 16). Die Carbonylierung von Ferralactonen fuhrt in aprotischen Losungsmitteln in guten Ausbeuten zu ungesattigten S-Lactonen (12). Am Isoprenepoxid wurde gezeigt, das auch die homogenkatalytische Cyclocarbonylierung von Vinyloxiranen gute Ausbeuten an δ-Lactonen ergibt und dieses Verfahren fur Synthesen von Interesse ist.



Organic Syntheses by Means of Transition Metal Complexes, 8 - Synthesis of Unsaturated δ-L-Lactones from Vinyloxiranes and Carbon Monoxide via Transition Metal Complexes



The transition metal-assisted carbonylation of vinyloxiranes to unsaturated δ-lactones has been verified and studied mechanistically by use of organometallic model reactions. The light induced complexation of vinyloxiranes 1 by Fe(CO)5 was shown to be a multistep reaction in which diastereomeric cis-resp. trans- ferralactones 2 are formed. Complexes of both types (2k, 2k′) were characterized crystallographically and studied chemically concerning their reactions with nucleophiles and electrophiles. Reaction with primary amines gives ferralactames 7 by migration of the allyl group and inversion at C-1 as well as C-4 indicating an attack of amine at the exo-position of C-4. On the other hand the reaction with HO⊖ leads to the formation of CO⊝ and diene complexes 10 with inversion at C-1 only, indicating that the reaction has been initiated by attack of HO⊖ at a terminal carbonyl group. On electrophilic attack ferralactones form allyl cations (14, 16) by opening of the CO – O bond. Carbonylation of ferralactones with CO in aprotic solvents give good yields of unsaturated δ-lactones (12). In the case of isoprene epoxide it has been shown that homogeneous catalytic cyclocarbonylation of vinyloxiranes can be of synthetic use.

Organische Synthesen mit Übergangsmetallkomplexen, 8. Untersuchungen zur Synthese ungesättigter δ-Lactone durch Cyclocarbonylierung von Vinyloxiranen mit Übergangsmetall-Komplexen

Lactones and Lactams by Light-Induced Reaction of 2-Vinyloxiranes and 2-Vinylaziridines with Pentacarbonyliron—Insertion of Carbon Monoxide into an Iron-Nitrogen σ Bond

δ-Lactones by Carbonylation of Vinyloxiranes†

Lactone und Lactame durch lichtinduzierte Reaktion von 2-Vinyl-oxiranen bzw. -aziridinen mit Pentacarbonyleisen – Kohlenmonoxid-Insertion in eine Eisen-Stickstoff-σ-Bindung

δ-Lactone durch Carbonylierung von Vinyloxiranen

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