Björn C.G. Söderberg

Palladium-catalyzed synthesis of 1,2-dihydro-4(3H)-carbazolones. Formal total synthesis of murrayaquinone A

Two sequential palladium-catalyzed reactions are the key steps in a novel synthetic route to 1,2-dihydro-4(3H)-carbazolones. The steps are an intermolecular Stille cross-coupling followed by a reductive N-heteroannulation. A formal total synthesis of murrayaquinone A, employing this sequence, is reported.

Transition metals in organic synthesis: highlights for the year 2000

A review with 1811 references about transition metal catalyzed or mediated reactions and functional group preparations is presented.

Palladium-catalyzed synthesis of fused indoles

Abstract A novel route to fused indoles via two consecutive palladium catalyzed reactions, an intramolecular Heck reaction followed by a reductive N-heteroannulation, has been developed. For example, reaction of 2-bromo-3-nitro-1-(3-butenyloxy)benzene with palladium diacetate, and tri(o-tolyl)phosphine in the presence of triethylamine gave a readily separable mixture (18:4:1) of dihydro-4-methylene-5-nitro-2H-1-benzopyran, 4-methyl-5-nitro-2H-1-benzopyran, and 4-methyl-5-nitro-4H-1-benzopyran. Reaction of pure dihydro-4-methylene-5-nitro-2H-1-benzopyran with palladium diacetate, 1,3-bis(diphenylphosphino)propane, and carbon monoxide in DMF (120 °C, 70 h, 60 psi CO) gave 3,5-dihydro-2H-pyrano[4,3,2-cd]indole in 63% yield.

A novel palladium-catalyzed synthesis of β-carbolines: application in total synthesis of naturally occurring alkaloids

Two naturally occurring β-carbolines, 6-methoxy-2-methyl-1,2,3,4-tetrahydro-β-carboline and bauerine A, have been prepared using a Stille-type coupling, followed by a palladium-phosphine catalyzed N-heteroannulation as the key steps.

Novel palladium-catalyzed synthesis of 1,2-dihydro-4(3H)-carbazolones

Two sequential palladium-catalyzed reactions are the key steps in a novel synthetic route to carbazolones, an intermolecular Stille coupling followed by a recently developed palladium-catalyzed reductive N-heteroannulation. A number of functionalized 1,2-dihydro-4(3H)-carbazolones were prepared using this sequence.

Synthesis of New Captodative Alkenes: Alkyl 2-Aroyloxy Acrylates − Structure, and Reactivity in Diels−Alder Cycloadditions

Novel captodative alkenes, namely the methyl and ethyl esters of 2-aroyloxyacrylic acids, 2 and 3, have been prepared. Their reactivity and selectivity have been evaluated in Diels−Alder cycloadditions with unsymmetrical dienes, which generate the corresponding adducts with high regioselectivity. No significant stereoselectivity was observed in the reaction with cyclopentadiene (9), although Lewis acid catalysis improved the exo/endo isomeric ratio. Structural and electron spectroscopic studies of these alkenes are supported by MO calculations. FMO theory accounts for the regioselectivity observed with isoprene (7), and the reactivity seen in Diels−Alder additions correlates with the stabilization of the relevant vacant π* MO in these alkenes, which is mainly due to the electron-withdrawing group.

Transition metals in organic synthesis: highlights for the year 1999

Abstract A review with 1621 references to transition metal catalyzed or mediated carbon–carbon bond forming reactions and functional group preparations.

Transition metals in organic synthesis: highlights for the year 2001

A review with 1663 references to transition-metal catalyzed or mediated reactions and functional group preparations.

Complete analysis of the 1H and 13C NMR spectra of diastereomeric mixtures of (R,S- and S,S-)-3,6-dimethoxy-2,5-dihydropyrazine-substituted indoles and their conformational preference in solution

Complete analysis of the 1H and 13C NMR spectra obtained with and without a chemical shift reagent (Eu(fod)3), of bis‐lactim ether 1 (Schöllkopf auxiliary) and monosubstituted 3‐ or 2‐{(2R,5S or 2S,5S)‐5‐isopropyl‐3,6‐dimethoxy‐2,5‐dihydropyrazin‐2‐yl]methyl}‐1H‐indoles is presented using gradient‐selected one‐dimensional (1D) and two‐dimensional NMR techniques, such as 1D TOCSY, 1D NOESY (DPFGSE NOE), gCOSY, NOESY, ROESY gHETCOR, gHSQC and gHMBC. The contour plot of the gCOSY spectrum of 1–10 revealed cross peaks arising from the five‐bond coupling between the H2 and H5 resonances of the dihydropyrazine ring for syn‐ (5JH2, H5 = 4–5.7 Hz) and for anti‐isomers (5JH2, H5 = 3.4–3.8 Hz). The magnitude of the coupling constant was utilized to distinguish between the syn‐ and the anti‐isomers (diastereomers). The precise values of nJHH (n = 3, 4, 5, 6) coupling constants for the indole and 2,5‐dihydropyrazine moieties deduced from the calculated NMR spectra were supported by 1D TOCSY and gCOSY experiments and gauge invariant atomic orbital (GIAO) calculations. The magnitude of the coupling constants (5JH2, H5) indicates that the dihydropyrazine ring exists in a boat conformation. In both isomers, the indole group adopts a ‘folded’ conformation in which one diastereotopic face is effectively shielded by the aromatic benzene ring of the indole. This is supported by gradient‐selected 1D NOESY and 2D NOESY experiments. Theoretical calculations of the conformation were performed to support the through‐space shielding effect of the aromatic indole moiety based on the DFT/GIAO calculated 1H NMR data (chemical shifts and coupling constants) for 2‐syn‐ and 2‐anti‐diastereomers in CDCl3. Copyright

Synthesis of 2‐Alkyl‐Substituted Benzimidazoles by Thermal Decomposition of 2‐Azidobenzenamines in thePresence of an Aldehyde

Abstract 2‐Substituted benzimidazoles were prepared by reaction of 2‐azidoaminobenzenes with aldehydes under thermal conditions. The reaction probably proceeds via a sequential imine formation, azide decomposition forming a nitrene, and electrocyclization.