Sequentielle Transformationen in der Organischen Chemie eine Synthesestrategie mit Zukunft

Reinvestigation of the reaction between 1,3-diketones and 2-hydroxyarylaldehydes: a short, atom-economical entry to tetrahydroxanthenones

A short and facile access to novel functionalized tetrahydroxanthenonesviaa DABCO-promoted tandem Knoevenagel condensation/hemiketalisation process from easily accessible substrates in a high yield.

Enantioselective total synthesis of the lignan (+)-linoxepin

An enantioselective total synthesis of the natural (+)-linoxepin (1) was accomplished in eleven steps from bromovanin (24). Key steps are a domino carbopalladation/ Mizoroki-Heck reaction with the formation of a pentacyclic system, an asymmetric hydroboration as well as an oxidative lactonization.

Diversity-oriented synthesis of intensively blue emissive 3-hydroxyisoquinolines by sequential Ugi four-component reaction/reductive Heck cyclization

A convergent approach to highly functionalized 3-hydroxyisoquinolines is reported. The key steps are an Ugi multicomponent reaction and a subsequent intramolecular reductive Heck reaction; these can also be performed as a one-pot procedure. The structures display very interesting properties as blue-fluorescence emitters. Photophysical studies on the absorption and static fluorescence indicate that the substitution pattern on the pyridyl part influences the optical properties only to a minor extent, unless the amide substituent becomes sterically demanding and leads to significant nonradiative deactivation. The donor substitution on the benzo core considerably enhances the fluorescence quantum yields and trimethoxy substitution causes a pronounced redshift of the emission bands. Protonation of the isoquinolyl nitrogen atom causes efficient static quenching of the fluorescence.

Crystal structure of (4-chloro-phen-yl)[2-(10-hy-droxy-phenanthren-9-yl)phenanthro[9,10-b]furan-3-yl]methanone

Mol­ecules of the title compound are arranged in the solid state in a three-dimensional supra­molecular architecture via inter­molecular O—H⋯O and C—H⋯O hydrogen bonding and through C—H⋯π inter­actions.

In the title compound, C₃₇H₂₁ClO₃, the dihedral angle between the two phenanthrene moieties is 57.79 (5)°. The furan and one of the phenanthrene groups are fused in an almost coplanar arrangement [dihedral angle = 5.14 (8)°] and the furan unit makes dihedral angles of 70.27 (11) and 57.58 (8)° with the planes of the phenyl and the second phenanthrene group, respectively. In the crystal, neighbouring mol­ecules are connected via two inter­molecular hydrogen-bonding inter­actions (O—H⋯O and C—H⋯O) towards the carbonyl O atom with donor–acceptor distances of 2.824 (2) and 3.277 (3) Å, creating an inversion dimer. A non-classical C—H⋯Cl inter­action [3.564 (2) Å] and three C—H⋯π inter­actions, with C⋯π distances of 3.709 (3), 3.745 (2) and 3.628 (3) Å, connect the mol­ecules, forming a three-dimensional supra­molecular architecture in the solid state.

Palladium-catalyzed chemoselective allylic substitution, Suzuki-Miyaura cross-coupling, and allene formation of bifunctional 2-B(pin)-substituted allylic acetate derivatives

A formidable challenge at the forefront of organic synthesis is the control of chemoselectivity to enable the selective formation of diverse structural motifs from a readily available substrate class. Presented herein is a detailed study of chemoselectivity with palladium-based phosphane catalysts and readily available 2-B(pin)-substituted allylic acetates, benzoates, and carbonates. Depending on the choice of reagents, catalysts, and reaction conditions, 2-B(pin)-substituted allylic acetates and derivatives can be steered into one of three reaction manifolds: allylic substitution, Suzuki-Miyaura cross-coupling, or elimination to form allenes, all with excellent chemoselectivity. Studies on the chemoselectivity of Pd catalysts in their reactivity with boron-bearing allylic acetate derivatives led to the development of diverse and practical reactions with potential utility in synthetic organic chemistry.

Toward a symphony of reactivity: cascades involving catalysis and sigmatropic rearrangements

Catalysis and synthesis are intimately linked in modern organic chemistry. The synthesis of complex molecules is an ever evolving area of science. In many regards, the inherent beauty associated with a synthetic sequence can be linked to a certain combination of the creativity with which a sequence is designed and the overall efficiency with which the ultimate process is performed. In synthesis, as in other endeavors, beauty is very much in the eyes of the beholder. It is with this in mind that we will attempt to review an area of synthesis that has fascinated us and that we find extraordinarily beautiful, namely the combination of catalysis and sigmatropic rearrangements in consecutive and cascade sequences.

Recent developments in one-pot tandem oxidation process coupling reactions

The recent additions to the tandem oxidation process (TOP) research area are reviewed.

An advanced and novel one-pot synthetic method for diverse benzo[c]chromen-6-ones by transition-metal free mild base-promoted domino reactions of substituted 2-hydroxychalcones with β-ketoesters and its application to polysubstituted terphenyls

Novel one-pot syntheses of a variety of benzo[c]chromen-6-one derivatives were accomplished by Cs₂CO₃-promoted reactions of 2-hydroxychalcones.

I2/O2-promoted domino reactions of isatins or 3-hydroxyindolin-2-one derivatives with enaminones

I2-promoted domino reactions of isatins or 3-hydroxyindolin-2-one derivatives with enaminones under O2 conditions have been established. The reactions of isatins with enaminones afforded functionalized tetracyclic pyrrolo[2,3,4-kl]acridine derivatives in moderate to good yields through domino cyclization and C-H oxidation. The reactions of 3-hydroxyindolin-2-one derivatives with enaminones proceeded well to give functionalized pyrrolo[2,3,4-kl]acridine derivatives via tandem ring-opening/recyclization/methyl migration sequences with two C-C bonds cleaved.

Enantioselective total synthesis of (-)-blennolide A

Blennolide A can be synthesized through an enantioselective domino-Wacker/carbonylation/methoxylation reaction of 7a with 96 % ee and an enantioselective Wacker oxidation of 7b with 89 % ee. Further transformations led to the α,β-unsaturated ester (E)-17, which was subjected to a highly selective Michael addition, introducing a methyl group to give 18a. After a threefold oxidation and an intramolecular acylation, the tetrahydroxanthenone 4 was obtained, which could be transformed into (-)-blennolide A (ent-1) in a few steps.