The first synthesis of the chromanone lactone dimer gonytolide A has been achieved employing vanadium(V)-mediated oxidative coupling of the monomer gonytolide C. An o-bromine blocking group strategy was employed to favor para- para coupling and to enable kinetic resolution of (±)-gonytolide C. Asymmetric conjugate reduction enabled practical kinetic resolution of a chiral, racemic precursor and the asymmetric synthesis of (+)-gonytolide A and its atropisomer.
Ab iomimetic route to farnesyl pyrophosphate and dimethyl orsellinic acid (DMOA)-derived meroterpenoid scaffolds has yet to be reported despite great interest from the chemistry and biomedical researchc ommunities.Aconcise synthetic route with the potential to access DMOA-derived meroterpenoids is highly desirable to create alibrary of related compounds.Herein, we report novel dearomatization methodology followed by polyene cyclization to access DMOAderived meroterpenoid frameworks in six steps from commercially available starting materials.F urthermore,s everal farnesyl alkene substrates were used to generate structurally novel, DMOA-derived meroterpenoid derivatives.D FT calculations combined with experimentation provided ar ationale for the observed thermodynamic distribution of polycyclization products. Figure 1. a) RepresentativeDMOA-derived meroterpenoid natural products. b) Biosyntheses of the DMOA-derived meroterpenoids.
The first Pd-pincer complex bearing a halogen (fluorine) arm has been prepared via the base-assisted dearomatization of a phosphine-quinoline (P~N) ligand. This dearomatization is reversible and has been used to facilitate catalytic Sonogashira-type cross-coupling that, contrary to the typical mechanistic approach, is based on a metal-ligand cooperation mode.
An arylpalladium PNF-type pincer complex reacts with water and anilines under very mild conditions, providing access to new PNO- and PNN-pincer complexes with concomitant hydrogen transfer to the ligand core. Such a metal-ligand cooperation mode allows for the irreversible double activation of even highly sterically hindered aniline molecules. With thiols, the activation mode depends on the nature of the substituent at the sulfur atom, with thiophenols giving products of C-S elimination.
An organometallic palladium(II) complex of an 8-fluoroquinoline-based chelating ligand undergoes very facile nucleophilic substitution of the "unactivated" fluorine atom with the methoxy group upon simple stirring of its THF solution with sodium methoxide at room temperature. The final product of this reaction lacks the aromaticity in the heterocyclic ring of the quinoline moiety which might play an important role in the overall reactivity.
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