Diazo reductive: a new approach to the synthesis of novel “upper rim” functionalized resorcin[4]arene Schiff-bases

The tetraaminoresorcin[4]arene was synthesized, which otherwise could not be easily synthesized by conventional method, by first introducing the azo group at the upper rim, followed by its reduction with Na₂S₂O₄. Tetraaminoresorcin[4]arene was then condensed with different aromatic aldehydes in ethanol at reflux temperature to obtain nine novel “upper rim” functionalized resorcin[4]arene Schiff-bases. All the nine Schiff-bases were characterized by m.p., elemental analysis, FT-IR, NMR and Mass spectral data.     

[Pd(PPh3)2(saccharinate)2]—general catalyst for Suzuki–Miyaura,Negishi cross-coupling and C–H bond functionalization of coumaryl and pyrone substrates

The potential of complex [Pd(PPh₃)₂(saccharinate)₂] 1 in catalyzing Suzuki–Miyaura cross-coupling of 4-halo and 4-bromomethyl coumaryl and pyrone substrates with different aryl boronic acids has been explored. Excellent yields of the desired products are obtained in competitive reaction time and under relatively mild conditions. Negishi cross-coupling of 4-coumaryl tosylate with aryl and alkylzinc reagents has also been performed with good yields of the cross-coupled products obtained in most cases. Intra-molecular C–H bond functionalization of coumaryl ethers also furnished very high yields of synthetically attractive tetracyclic ring systems exhibiting the potential of 1 as a powerful catalyst in synthetically important reactions.     

On the proximal point method in Hadamard spaces

Proximal point method is one of the most influential procedure in solving nonlinear variational problems. It has recently been introduced in Hadamard spaces for solving convex optimization, and later for variational inequalities. In this paper, we study the general proximal point method for finding a zero point of a maximal monotone set-valued vector field defined on a Hadamard space and valued in its dual. We also give the relation between the maximality and Minty’s surjectivity condition, which is essential for the proximal point method to be well-defined. By exploring the properties of monotonicity and the surjectivity condition, we were able to show under mild assumptions that the proximal point method converges weakly to a zero point. Additionally, by taking into account the metric subregularity, we obtained the local strong convergence in linear and super-linear rates.     

Synthesis of bavachromanol from resorcinol via a tandem cationic cascade/EAS sequence

The natural chalcone bavachromanol has been prepared through a tandem reaction sequence that joins cationic cyclization of an epoxide to an adjacent MOM-acetal with electrophilic aromatic substitution by a presumed methoxymethylene cation. Only a single regioisomer of the tandem product was observed, with substitution taking place exclusively ortho to the position of the original acetal. This regiocontrol provided a key intermediate from a symmetrical precursor, and allowed preparation of the meroterpenoid through a short reaction sequence.