No abstract

In this paper, we used bond-length equalization, aromatic stabilization energies (ASE) and nucleusindependent chemical shifts (NICS), calculated with (density functional theory) B3LYP levels at the 6-311 + G * * basis set, to evaluate the aromaticity of a set of 38 five-member planar π -electron aromatic systems: sila-, aza-and phosphaderivatives and their parent systems. The result revealed statistically significant correlations among the above three criteria, and the order of aromaticity of the whole set was: Aza-derivatives rings > Phospha-derivatives rings > Siladerivatives rings > Carbon-containing rings; NICS(0.6) and NICS(0.8) had the same results in evaluating the order of aromaticity in our case.

Ring expansion reactions have been proven to be efficient tools for building medium-sized rings with broad applications in synthetic and medicinal chemistry. However, the strategy involving pericyclic or pseudopericyclic pathways via sulfur ylide-initiated [1,4]-sigmatropic rearrangement remains an under-exploited area. Herein, we disclose an interesting ring expansion of thiochromenes and aromatic thiophenes via rhodium catalysis, which enables the straightforward assembly of polyaromatic oxathionines and oxathiocines with diverse functionalities. The mechanistic investigation via DFT calculations revealed this ring expansion transformation to be a [1,4]-sigmatropic rearrangement via a metal-free sulfur-based ylide.

Six rearranged sesquiterpenoid dimers and monomers with four kinds of new skeletons, meso-eugenunilone A (meso-1), (+)- and (-)-eugenunilones B-F [(+)-and (-)-2-6], along with two new biogenetically related members (+)- and...

Diverse naphthoquinone-containing heterocycle synthesis has been developed via enol/enolate-directed palladium catalytic processes together with late-stage functionalization and lead compound development.