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Ferrocenyl conjugated oxazepine/quinoline derivatives were presented through the reaction of hexadehydro-Diels-Alder (HDDA) generated arynes with ferrocenyl oxazolines under mild conditions via ring-expanding or rearrangement processes. Water molecule participated in this unexpected rearrangement process to produce quinoline skeletons, and DFT calculations supported a ring-expanding and intramolecular hydrogen migration process for the formation of oxazepine derivatives. Two variants of this chemistry, expanded the reactivity between ferrocenyl conjugated substances and arynes, further providing an innovative approach for the synthesis of ferrocene derivatives. [ABSTRACT FROM AUTHOR]

Two new chiral 1,2,3‐triazole‐containing macrocyclic oligoamides (i. e.: triazolopeptoid 4 and 5) were obtained through solid‐phase synthesis of linear precursors followed by high dilution macrocyclization reaction. Theoretical (DFT) and spectroscopic (NMR) studies revealed the intricate interplay between the Nα‐chiral side chains and their conformational attitudes. BH3‐mediated reduction of the tertiary amide groups of known 1–3 and newly synthesized 4 gave novel azamacrocycles 6–9. Detection of borane complexes of azamacrocycles 6 and 9 (i. e.: 10 and 11), corroborated by X‐ray diffraction studies, demonstrated the peculiar properties of 1,2,3‐triazole‐containing macrorings. [ABSTRACT FROM AUTHOR]

This review describes the advances of heterogenous phase‐transfer catalysts onium‐based and their importance from a sustainable point of view. Although heterogeneous phase‐transfer catalysts have shown incredible advantages in many organic reactions, examples of supported phase‐transfer catalysts onium‐based are still limited. In this review, we will examine the most common supports, including polymers, clays, and inorganic materials. Additionally, new recent developments in carbon materials application as efficient heterogeneous phase‐transfer catalysts in water will be reported, opening a new route toward green and sustainable procedures. Furthermore, considering the ever‐growing interest in asymmetric synthesis we wish to discuss the important achievements in the field of chiral heterogeneous phase‐transfer catalysts. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) is a common medical imaging technique that provides three‐dimensional body images. MRI contrast agents improve image contrast by raising the rate of water proton relaxation in specific tissues. Peptides and peptidomimetics act as scaffolds for MRI imaging agents because of their increased size and offer the possibility to engine a higher hydration value within the design. The design of a new Gd‐based contrast agent must take into account high stability constants to avoid free Gd(III), with the subsequent nephrotoxicity, and high relaxivity values. This review analyzes various synthetic approaches, reports studies of relaxometric parameters, and focuses on the description and application of Gd(III)‐chelates based on peptide and peptidomimetic scaffolds. In addition, the X‐ray molecular structures of three DOTA complexes will be reported to emphasize the necessity of using the X‐ray diffraction analysis to identify the coordination sphere of the metals and the mechanism of action of the compounds. [ABSTRACT FROM AUTHOR]

Chiral β-azido- and β-cyanocarbonyl compounds are extremely useful building blocks in asymmetric synthesis, thanks to the manyfold reactivity of their functional groups. The enantioselective synthesis of such compounds, until the beginning of the 21st century, has been mostly achieved using transition-metal chiral catalysts. The explosion of enantioselective organocatalysis, however, has enabled the development of efficient metal-free methodologies with significant benefits in terms of costs and environmental safety. An overview of the advances made in recent years in this field is herein presented. [ABSTRACT FROM AUTHOR]

Cyclic peptoids are biocompatible/biodegradable cyclooligomers constituted by N-substituted glycines showing high binding constants with the first group alkali metals (Ka ∼ 106 for Na+, Li+ and K+) in organic solvents. Three new metallated species bearing N-benzyl groups as side chains (a cyclic pentamer, [1·2Na]2+, and two cyclooctamer [3·Na]+ and [3·2Na]2+ peptoids) were synthesized together with the known N-perbenzylated sodiated cyclohexamer [2·Na]+ and [2·2Na]2+. Na+ complexes were investigated by means of spectroscopic (NMR), computational (DFT) and X-ray crystallographic studies. The first application of these complexes as catalysts in the ring opening polymerization (ROP) of L -lactide (L -LA) was examined. Our studies suggest that, for the intrinsic properties of the catalytic site (revealed by steric topographic maps) the homooligomeric pentamer complex [1·2Na]2+ is the most active member of the cyclooligomeric family. [ABSTRACT FROM AUTHOR]

Two families of hexameric cyclic peptoids decorated with linear N‐alkyl and alternated N‐alkyl/N‐benzyl side chains (2 a–d and 3 a–c, respectively) were designed and synthesized in order to correlate their logP values (from 2.55 to 6.83) to their ionophoric activities. The present contribution confirms the general ability of hexameric cyclic peptoids to behave as efficient cation carriers, corroborates their preference for Na+ ion, among the tested alkali metals, and suggests a Na+/H+ antiport transport mechanism (rate limited by the transport of the proton) for these new ionophores. Our observations indicate that in order to attain an efficient ionophoric activity, a narrow range of liphophilicity is required (4