Unusual Regio- and Chemoselectivity in Oxidation of Pyrroles and Indoles Enabled by a Thianthrenium Salt Intermediate.

A dearomative oxidation of pyrroles to Δ-pyrrol-2-ones is described, which employs a sulfoxide as oxidant, in conjunction with a carboxylic acid anhydride and a Brønsted acid additive. 3-substituted pyrroles undergo regioselective oxidation to give the product isomer in which oxygen has been introduced at the more hindered position. Regioselectivity is rationalized by a proposed mechanism that proceeds by initial thianthrenium introduction at the less-hindered pyrrole α-position, followed by distal attack of an oxygen nucleophile and subsequent elimination of thianthrene.

Synthesis of -alkoxycarbonyl Pyrroles from -Substituted Carbamates: A Synthetically Enabling Pyrrole Protection Strategy.

The condensation of readily available -substituted carbamates with 2,5-dimethoxytetrahydrofuran gives -alkoxycarbonyl pyrroles in a single step and in good yield. By this method, several common amine protecting groups can be introduced on the pyrrole nitrogen. With the exception of -Boc, -alkoxycarbonyl groups have seen only minimal use for protection of the pyrrole nitrogen to date.

Influence of Thermal and Flash-Lamp Annealing on the Thermoelectrical Properties of CuZnSnS Nanocrystals Obtained by "Green" Colloidal Synthesis.

The problem with waste heat in solar panels has stimulated research on materials suitable for hybrid solar cells, which combine photovoltaic and thermoelectric properties. One such potential material is CuZnSnS (CZTS). Here, we investigated thin films formed from CZTS nanocrystals obtained by "green" colloidal synthesis.

Raman Spectroscopy and Thermoelectric Characterization of Composite Thin Films of CuZnSnS Nanocrystals Embedded in a Conductive Polymer PEDOT:PSS.

CuZnSnS (CZTS) is an intensively studied potential solar cell absorber and a promising thermoelectric (TE) material. In the form of colloidal nanocrystals (NCs), it is very convenient to form thin films on various substrates. Here, we investigate composites of CZTS NCs with PEDOT:PSS, a widely used photovoltaics polymer.

Persistent azulene α-carbocations: synthesis from aldehydes, spectroscopic and crystallographic properties.

The non-benzenoid aromatic system azulene is sufficiently nucleophilic at C1 that it can react with a protonated aldehyde to form an α-azulenyl alcohol. This in turn may be protonated and undergo loss of water to give an azulene α-carbocation. We report the isolation of such azulenyl cations as salts with non-coordinating anions.