: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Late transition metal-catalyzed hydroamination and hydroamidation.

The use of coordinating moieties as directing groups for the functionalisation of aromatic carbon–hydrogen (C–H) bonds has become an efficient strategy for the selective construction of new carbon–carbon (C–C) and carbon–heteroatom (C–X) bonds in arenes. However many directing groups cannot be easily removed/modified from the products after C–H functionalisation, thus limiting the structural diversity of the products. This limitation can be overcome by employing removable/modifiable or traceless directing groups which can be easily attached to the starting materials and detached from the products. In this tutorial review, we give an overview of recent advances in this emerging field which have dramatically increased the synthetic applicability of C–H functionalisation processes.

Arene C–H functionalisation using a removable/modifiable or a traceless directing group strategy

Silver is a less expensive noble metal. Superior alkynophilicity due to π-coordination with the carbon-carbon triple bond makes silver salts ideal catalysts for alkyne-based organic reactions. This review highlights the progress in alkyne chemistry via silver catalysis primarily over the past five years (ca. 2010-2014). The discussion is developed in terms of the bond type formed with the acetylenic carbon (i.e., C-C, C-N, C-O, C-Halo, C-P and C-B). Compared with other coinage metals such as Au and Cu, silver catalysis is frequently observed to be unique. This critical review clearly indicates that silver catalysis provides a significant impetus to the rapid evolution of alkyne-based organic reactions, such as alkynylation, hydrofunctionalization, cycloaddition, cycloisomerization, and cascade reactions.

Silver-catalysed reactions of alkynes: recent advances

This review is focused on the analysis of current data on new methods of alkenylation of arenes and heteroarenes with alkynes by transition metal catalyzed reactions, Bronsted/Lewis acid promoted transformations, and others. The synthetic potential, scope, limitations, and mechanistic problems of the alkenylation reactions are discussed. The insertion of an alkenyl group into aromatic and heteroaromatic rings by inter- or intramolecular ways provides a synthetic route to derivatives of styrene, stilbene, chalcone, cinnamic acid, various fused carbo- and heterocycles, etc.

Alkenylation of Arenes and Heteroarenes with Alkynes.

The first general protocol for the synthesis of unprotected indoles via the title reaction is presented.

General and Efficient Synthesis of Indoles through Triazene‐Directed C–H Annulation

We described two orthogonal heterocycle syntheses, where an arene bearing both an alkyne and a triazene functionality underwent two distinct cyclization pathways mediated by different transition metals. Starting from the same substrates, a synthesis of 2H-indazole was accomplished by a Cu(II) salt promoted oxidative cyclization, while 2-substituted indoles could be accessed via a Ag(I) salt mediated N–N bond cleavage. This method represents the first synthesis of indoles from alkynyl triazenes. Computational analysis was performed for both reaction pathways, supporting a Lewis acid role for Cu and a π-acid catalysis for Ag.

Selective synthesis of indazoles and indoles via triazene–alkyne cyclization switched by different metals

Polyol-substituted cyclic ethers are fundamental building blocks of biomolecules. The position and stereochemistry of multiple hydroxy substituents of cyclic ethers play a central role in their biological function. Current methods for the synthesis of such structures are limited to "naked" ring products with no or few substituents. Here we describe a general route to medium-sized polyol cyclic ethers using a migratory ether formation strategy. In contrast to the common pathway of direct opening of epoxides, Me3 Al was found to promote an unprecedented ether addition reaction, opening a neighboring epoxide. The resulting oxonium intermediate triggers a 1,3-methyl shift to yield 2-deoxyribital products. When the hemiacetal auxiliary is a monosaccharide, the sugar ring is expanded by four atoms to give the corresponding 9- to 11-membered analogues. This method provides an entry into the untapped chemical space of medium-sized sugar mimetics.

A Migratory Ether Formation Route to Medium-Sized Sugar Mimetics.

General and Efficient Synthesis of Indoles Through Triazene‐Directed C—H Annulation.

The copper-mediated oxidative cyclization of alkynyl triazenes (I) leads to indazoles of type (II), whereas, the silver-mediated reaction affords indoles of type (IV).

Yan Fang

Papers

General and Efficient Synthesis of Indoles through Triazene‐Directed C–H Annulation

Selective synthesis of indazoles and indoles via triazene–alkyne cyclization switched by different metals

A Migratory Ether Formation Route to Medium-Sized Sugar Mimetics.

General and Efficient Synthesis of Indoles Through Triazene‐Directed C—H Annulation.

Selective Synthesis of Indazoles and Indoles via Triazene—Alkyne Cyclization Switched by Different Metals.