Ring formation (Chemistry) -- Research, Diels-Alder reaction -- Research, Chemistry, Organic -- Research, and Chemical research

Cycloaddition reactions provide direct and convergent routes to cycloalkanes, making them valuable targets for the development of synthetic methods. Whereas six-membered rings are readily accessible from Diels-Alder reactions, cycloadditions that generate five-membered rings are comparatively limited in scope. Here, we report that dinickel complexes catalyze [4 + l]-cycloaddition reactions of 1, 3-dienes. The Ci partner is a vinylidene equivalent generated from the reductive activation of a 1, 1-dichloroalkene in the presence of stoichiometric zinc. Intermolecular and intramolecular variants of the reaction are described, and high levels of asymmetric induction are achieved in the intramolecular cycloadditions using a [C.sub.2]-symmetric chiral ligand that stabilizes a metal-metal bond.

Catalysis -- Analysis, Light -- Analysis, and Chemistry, Organic -- Analysis

Author(s): Mattia Silvi [1]; Paolo Melchiorre (corresponding author) [2, 3] The preparation of chiral molecules with a well-defined, three-dimensional spatial arrangement is central to synthetic chemistry. Enantioselective organocatalysis offers powerful [...]
Organocatalysiscatalysis mediated by small chiral organic moleculesis a powerful technology for enantioselective synthesis, and has extensive applications in traditional ionic, two-electron-pair reactivity domains. Recently, organocatalysis has been successfully combined with photochemical reactivity to unlock previously inaccessible reaction pathways, thereby creating new synthetic opportunities. Here we describe the historical context, scientific reasoning and landmark discoveries that were essential in expanding the functions of organocatalysis to include one-electron-mediated chemistry and excited-state reactivity.

Carbon -- Research, Chemistry, Organic -- Research, Substrates (Biochemistry) -- Research, and Chemical research

Author(s): Rohan E. J. Beckwith The basis of organic chemistry is the study of carbon-containing compounds with the aim of manipulating carbon atoms to generate new molecules through the formation [...]

Radicals (Chemistry) -- Analysis, Chemistry, Organic -- Analysis, and Carbon -- Chemical properties

An important goal of modern organic chemistry is to develop new catalytic strategies for enantioselective carbon-carbon bond formation that can be used to generate quaternary stereogenic centres. Whereas considerable advances [...]

Chemistry, Organic -- Research, Chemical synthesis -- Methods, and Chemical research

Peptides -- Chemical properties, Peptides -- Spectra, Heterocyclic compounds -- Chemical properties, Chemistry, Organic -- Research, and Carbohydrates -- Chemical properties

The preferential stabilization (10) of pyranose sugar rings when they contain an axial electronegative substituent at C1 (Fig. 1a) is contrary to expectations based on considerations of steric or solvation [...]
The anomeric effect is a chemical phenomenon (1-9) that refers to an observed stabilization (10) of six-membered carbohydrate rings when they contain an electronegative substituent at the C1 position of the ring. This stereoelectronic effect influences the three-dimensional shapes of many biological molecules. It can be manifested not only in this classical manner involving interaction of the endocyclic oxygen atom (O5) found in such sugars with the C1 substituent (endo-anomeric effect) but also through a corresponding interaction of the electronegative exocyclic substituent with O5 (exo-anomeric effect). However, the underlying physical origin(s) of this phenomenon is still not clear (1,3,4,11-14). Here we show, using a combination of laser spectroscopy and computational analysis, that a truncated peptide motif can engage the two anomers of an isolated sugar in the gas phase, an environment lacking extraneous factors which could confound the analysis. (Anomers are isomers that differ in the orientation of the substituent at C1.) Complexes formed between the peptide and the [alpha]- or [beta]-anomers of D-galactose are nearly identical structurally; however, the strength of the polarization of their interactions with the peptide differs greatly. Natural bond order calculations support this observation, and together they reveal the dominance of the exo- over the endo-anomeric effect. As interactions between oxygen atoms at positions C1 and C2 (O1 and O2, respectively) on the pyranose ring can alter the exo/endo ratio of a carbohydrate, our results suggest that it will be important to reevaluate the influence, and biological effects, of substituents at position C2 in sugars.

Chemistry, Organic -- Research, Chemical bonds -- Research, and Chemical research

Author(s): Kin S. Yang [1]; Keary M. Engle (corresponding author) [1] For much of the past century, organic chemists have focused on the reactions of functional groups: arrangements of atoms [...]

Market trend/market analysis, Nanotubes -- Properties, Graphene -- Properties, Chemistry, Organic -- Forecasts and trends, and Chemistry, Organic -- Economic aspects

In fairy tales, third place is often the best: it's usually the third casket that contains the treasure, and the third child who finds fame and fortune. And so it [...]

Radicals (Chemistry) -- Properties, Olefins -- Chemical properties, and Chemistry, Organic

Author(s): Steven L. Castle (corresponding author) [1] Reactions that form carbon-carbon (C-C) bonds are essential for synthesizing complex organic molecules from simple, inexpensive precursors. The value that such molecules have [...]

Microbial enzymes -- Research, Chemical synthesis -- Analysis, and Chemistry, Organic -- Analysis

The metabolism of living organisms could be harnessed to help construct small molecules, according to a team from Harvard University in Cambridge, Massachusetts. Chemists routinely use microbial enzymes as catalysts. [...]

Chemical synthesis -- Research, Chemistry, Organic -- Research, and Second messengers (Biochemistry) -- Research

Chemical messengers called prostaglandins are present in nearly all mammalian tissues. These elusive molecules mediate an extraordinary number of biological processes--including the regulation of body temperature, the contraction and relaxation [...]

Medical publishing -- Analysis, Chemistry, Organic -- Analysis, and Research grants

Change comes slowly in China and necessary change to the way Chinese science works is coming very slowly indeed. Despite suggestions earlier this year that reform was in the air, [...]