Chiroptical studies on brevianamide B: vibrational and electronic circular dichroism confronted.

Chiroptical spectroscopies, such as electronic circular dichroism (ECD) and vibrational circular dichroism (VCD), are highly sensitive techniques to probe molecular conformation, configuration, solvation, and aggregation. Here we report the application of these techniques to study the fungal metabolite brevianamide B. Comparison of the experimental ECD and VCD spectra with the density functional theory simulated counterparts establishes that VCD is the more reliable technique to assign absolute configuration due to the larger functional and dispersion dependence of computed ECD spectra. Despite a low amount of available material and a relatively unusual example of using VCD carbonyl multiplets, the absolute configuration could be reliably predicted, strengthening the case for application of VCD in the study of complex natural products. Spectral and crystallographic evidence for or against the formation of a dimeric aggregate is discussed; in solution, the VCD spectra strongly suggest only monomeric species are present.

Stoichiometric C-H arylation of tricarbonyl(arene)chromium complexes bearing pyridine directing groups.

Differentially substituted Cr(CO)3-complexed aryl pyridines have been shown to readily undergo stoichiometric palladation and subsequent arylation using boronic acid nucleophiles. The positioning of the aryl substituents has been shown to be key in governing substrate reactivity, whereby sterically congested compounds prevent the geometry required for cyclometallation.

A scalable and expedient route to 1-aza[6]helicene derivatives and its subsequent application to a chiral-relay asymmetric strategy.

A rapid route to diversely functionalized 1-aza[6]helicenes has been achieved via the development of a copper-mediated cross-coupling reaction, followed by PtCl4-catalyzed cycloisomerization. Not only does this method allow access to these functionally important molecules on gram scale, but this strategy is also suitable for relaying the axial chirality of a key intermediate to the helicity of the product.

Synthesis of sterically encumbered C10-arylated benzo[h]quinolines using ortho-substituted aryl boronic acids.

The challenging coupling of 10-halobenzo[h]quinolines with ortho-substituted aryl boronic acids has been achieved using Pd(OAc)(2)/P(O)Ph(3) as the catalytic system. High yields were obtained for diversely functionalised substrates under mild reaction conditions.

[7]-Helicene: a chiral molecular tweezer for silver(I) salts.

We have unambiguously demonstrated the binding of the silver(I) ion in the central cavity of [7]-helicene, given that the counterion is weakly coordinating. In such a binding mode, the helicene is functioning as a chiral molecular tweezer.

Enantioselective synthesis of (+)-estrone exploiting a hydrogen bond-promoted Diels-Alder reaction.

Starting from Dane's diene and methylcyclopentenedione, (+)-estrone is synthesized along the Quinkert-Dane route in 24% total yield. The key step is an enantioselective Diels-Alder reaction promoted by an amidinium catalyst as efficiently as by a traditional Ti-TADDOLate Lewis acid.