Palladium-catalyzed coupling of N-tosylhydrazones with ortho substituted aryl halides: synthesis of 4-arylchromenes and related heterocycles (original) (raw)
Related papers
Advanced Synthesis & Catalysis, 2010
Two different combinations of coupling partners can be employed for the synthesis of conjugated dienes by palladium-catalyzed cross-coupling with tosylhydrazones: a,b-unsaturated ketone and aryl halide or alkenyl halide and non-conjugated tosylhydrazone. Depending on the substrate, a vinylogous hydride elimination is responsible for the formation of the final dienes.
Synthesis of Five- and Six-Membered Heterocycles Through Palladium-Catalyzed Reactions
ChemInform, 2004
Over the last years, palladium-catalyzed coupling reactions have been extensively studied and the names of Heck, Stille, Suzuki and Sonogashira are well known for their contribution to this chemistry. Extension of the coupling reactions allowing introduction of heteroatoms have followed and the Buchwald-Hartwig reaction is now a concept for this chemistry. Another achievement in this field is the possibility offered by the methodology to acceed to heterocyclic compounds either through a direct construction of the heterocyclic ring or by a two-step procedure (coupling followed by an heteroannulation). We are in the following paper going to review these ways of preparing heteroaromatic compounds either as single ring system or condensed to other aromatic rings. I) PREPARATION OF FIVE-MEMBERED AROMATIC HETEROCYCLES IN A ONE-STEP PROCEDURE I-1) Synthesis of Pyrroles The Sonogashira coupling of an alkyne chain containing a tosylhydrazone (1) with aryl iodides led to the formation of 2-benzylsubstituted pyrroles (2) in 40-70% yield; in the absence of aryl iodide, 2-methylsubstituted pyrroles were obtained [1].
Pyridine-Hydrazone Ligands in Asymmetric Palladium-Catalyzed 1,4- and 1,6-Additions of Arylboronic Acids to Cyclic (Di)enones., 2019
Catalysts generated by combinations of Pd(TFA) 2 and enantiomerically pure pyridine-hydrazone ligands have been applied to the 1,4-addition of arylboronic acids to b-substituted cyclic enones, building all-carbon quaternary stereocenters in high yields and enantioselectivities (up to 93% ee). The developed methodology allows the efficient introduction of ortho-substituted aryl groups in b-position of cyclopentanone cores, giving scaffolds present in a broad range of biologically active natural products. These Pd(II)-complexes served also as catalysts in the 1,6-addition of arylboronic acids to cyclic dienones, affording complete regioselectivities, moderate yields and good enantioselectivities (up to 80% ee).
Synthesis of Functionalized Triphenodioxazines via Palladium Catalyzed Cross-Coupling Reactions
Asian Journal of Chemistry
The synthesis of phenoxazine derivatives and the isolation of natural phenoxazinones [1] have been a subject of continuing interest over the years due to the wide range of applications of these compounds. Notable among the natural products derived from phenoxazine ring skeleton are actinomycin [2] antibiotics isolated from streptomyces organisms, ommatin D [3], the redbrown pigment isolated from small tortoiseshell butterfly, Vanessa aurticae, the questiomycines [4-6] from Waksmania aerate and Pseudomonas iodinum and the cinnabarins [7,8] from wood-rotting fungi, Coriolus sanquineus and Trametes cinabarina. Apart from questiomycin and actinomycin antibiotics, which are notable for their antituberculosis and antitumor action, respectively. Most known phenoxazinones are pigments in their natural sources although some of them have been synthetically modified to be applicable as dyes [9-11]. In view of the reports [12-18] on the pharmacological activities of phenothiazines and phenoxazines, attention was shifted from their dyeing properties to a study of their biological activities. Phenothiazines and phenoxazines ring systems are vital component of various drugs used as antitumor agents,