Studies in electrophilic cyclization, palladium migration and cationic polymerization

2,3-Disubstituted benzo[b]selenophenes have been prepared by the electrophilic cyclization of various 1-(1-alkynyl)-2-(methylseleno)arenes by Br2, NBS, I2, ICl, PhSeCl, PhSeBr and Hg(OAc) 2. This method tolerates a wide variety of functional groups, including alcohol, ester, nitrile, nitro and silyl groups, and proceeds under exceptionally mild reaction conditions. A cationic intermediate in the cyclization with Br2 has been isolated and studied, providing evidence for a stepwise cyclization process

MP2-F12 Basis Set Convergence for the S66 Noncovalent Interactions Benchmark: Transferability of the Complementary Auxiliary Basis Set (CABS)

Complementary auxiliary basis sets for F12 explicitly correlated calculations appear to be more transferable between orbital basis sets than has been generally assumed. We also find that aVnZ-F12 basis sets, originally developed with anionic systems in mind, appear to be superior for noncovalent interactions as well, and propose a suitable CABS sequence for them.Comment: AIP Conference Proceedings, in press (ICCMSE-2017 proceedings), 4 page

BLENDED LEARNING: NEED OF THE HOUR WITH SPECIAL REFERENCE TO THE INDIAN EDUCATION SYSTEM

Blended learning is a method that combines traditional classroom teaching and online instruction to create an enhanced educational environment. It aims to blend the best practices of both offline and online pedagogies, benefiting from the strengths of conventional instructional methods and modern digital approaches. It also supports the idea of creative learning and Computer-Assisted Instruction (CAI). Successful implementation of blended learning requires dedicated efforts, proper planning, good execution, and the involvement of proficient educators and students. As it involves various stakeholders, it can be complex and requires careful handling

The S66 noncovalent interactions benchmark reconsidered using explicitly correlated methods near the basis set limit

The S66 benchmark for noncovalent interactions has been re-evaluated using explicitly correlated methods with basis sets near the one-particle basis set limit. It is found that post-MP2 "high-level corrections" are treated adequately well using a combination of CCSD(F12*) with (aug-)cc-pVTZ-F12 basis sets on the one hand, and (T) extrapolated from conventional CCSD(T)/heavy-aug-cc-pV{D,T}Z on the other hand. Implications for earlier benchmarks on the larger S66x8 problem set in particular, and for accurate calculations on noncovalent interactions in general, are discussed. At a slight cost in accuracy, (T) can be considerably accelerated by using sano-V{D,T}Z+ basis sets, while half-counterpoise CCSD(F12*)(T)/cc-pVDZ-F12 offers the best compromise between accuracy and computational cost.Comment: Australian Journal of Chemistry, in press [Graham S. Chandler special issue

Solvent Effects on the Stereoselectivity of Reaction of Methyl Acrylate, Methyl Methacrylate and Methyl trans-Crotonate with Cyclopentadiene: A Computational Study

The stereoselectivity of reaction of methyl acrylate, methyl methacrylate and methyl transcrotonate with cyclopentadiene was studied with ab initio RHF/6-31G* and B3LYP/6-31G* levels of theory. The stereoselectivities predicted for methyl acrylate and methyl methacrylate with cyclopentadiene in the gas phase were found to be in good agreement with experimental results. The preference of endo selectivity in solvents was more pronounced for methyl acrylate, however, the preference for the exo-addition for methyl methacrylate was predicted to be reduced in solvents. The solvent calculations predicted the endo- preference for methyl trans-crotonate in agreement with the experimental observations. The lower endo selectivity for methyl trans-crotonate with cyclopentadiene seems to be governed by the degree of asynchronicity of endo- and exo-transition states in water. B3LYP/6-31G* calculated activation enthalpy was found to be in good agreement with the observed activation enthalpy for methyl acrylate and cyclopentadiene, however, this method does not predict the stereoselectivities correctly in all cases. The hydrogen bonding between water and polarized transition states seems to be important for rate acceleration in wate