Search results for "Organic"

Back Cover: Water Structure Recovery in Chaotropic Anion Recognition: High-Affinity Binding of Dodecaborate Clusters to γ-Cyclodextrin (Angew. Chem. …

2015

Desymmetrization of Prochiral Cyclobutanones via Nitrogen Insertion: A Concise Route to Chiral γ‐Lactams

2021

Abstract Asymmetric access to γ‐lactams is achieved via a cyclobutanone ring expansion using widely available (1S,2R)‐1‐amino‐2‐indanol for chiral induction. Mechanistic analysis of the key N,O‐ketal rearrangement reveals a Curtin–Hammett scenario, which enables a downstream stereoinduction (up to 88:12 dr) and is corroborated by spectroscopic, crystallographic, and computational studies. In combination with an easy deprotection protocol, this operationally simple sequence allows the synthesis of a range of optically pure γ‐lactams, including those bearing all‐carbon quaternary stereocenters. In addition, the formal synthesis of drug molecules baclofen, brivaracetam, and pregabalin further …

A 2600-year record of past polycyclic aromatic hydrocarbons (PAHs) deposition at Holzmaar (Eifel, Germany)

2014

Polycyclic aromatic hydrocarbons (PAHs) are a proxy for climate- and human-related historical fire activity which has rarely been used beyond 1800 AD. We explored the concentration and composition patterns of PAHs together with other proxies (charcoal, C, N, S, δ13C, δ15N, and δ34S) in a sediment core of Holzmaar as indicators of variations in climate and anthropogenic activity over the past 2600 years. The concentrations of pyrogenic PAHs remained low (< 500 ng g− 1) from the pre-Roman Iron Age (600 BC) until the first significant increases to ca. 1000–1800 ng g− 1 between 1700 and 1750 AD related to regional iron production. The highest increases in pyrogenic PAH concentrations occurred w…

Crystal structures of 4-chloro-pyridine-2-carbo-nitrile and 6-chloro-pyridine-2-carbo-nitrile exhibit different inter-molecular π-stacking, C-H⋯Nnitr…

2015

The crystal structures of two chloro­cyano­pyridines, namely 4-chloro­pyridine-2-carbo­nitrile and 6-chloro­pyridine-2-carbo­nitrile, exhibit unique inter­molecular C—H⋯Nnitrile, C—H⋯Npyridine and offset face-to-face π-stacking inter­actions.