Synlett

Quinolines, especially 2-aminoquinolines, are highly important heterocycles in medicinal chemistry. 2-Aminoquinolines can be synthesized by stepwise construction of the quinoline ring followed by additional amination; however, this protocol is cumbersome. Here, we describe a [5+1]-cyclization of 2-vinylanilines with tetraalkylthiuram disulfides in the presence of iodine and copper(II) triflate. This reaction directly employs readily available and low-cost thiuram as both a C1 synthon and a nitrogen source, providing a facile approach to one-step syntheses of a variety of 2-aminoquinolines in good to excellent yields.

Trivalent-phosphorus-containing molecules are widely used in fields ranging from catalysis to materials science. Efficient catalytic methods for their modifications, providing straightforward access to novel hybrid structures with superior catalytic activities, are highly desired to facilitate reaction improvement or discovery. We have recently developed new methods for synthesizing polyfunctional phosphines by C–C cross-couplings through rhodium-catalyzed C–H bond activation. These methods use a native P(III) atom as a directing group, and can be used in regioselective late-stage functionalization of phosphine ligands. Interestingly, some of the modified phosphines outperform their parents in Pd-catalyzed cross-coupling reactions.1 Introduction2 Early Examples of Transition-Metal-Catalyzed P(III)-Directed C–H Bond Activation/Functionalizations3 Synthesis of Polyfunctional Biarylphosphines by Late-Stage Alkylation: Application in Carboxylation Reactions4 Synthesis of Polyfunctional Biarylphosphines by Late-Stage Alkenylation: Application in Amidation Reactions5 Conclusion

Quantitative and real-time characterization of mechanically induced bond-scission events taken place in polymeric hydrogels is essential to uncover their fracture mechanics. Herein, a class of mechanochemiluminescent swelling hydrogels have been synthesized through a facile micellar copolymerization method using chemiluminescent bisacrylate-modified bis(adamantyl)-1,2-dioxetane (Ad) as a crosslinker. This design and synthetic strategy ensure intense mechanochemiluminescence from Ad located in a hydrophobic network inside micelles. Moreover, the mechanochemiluminescent colors can be tailored from blue to red by mixing variant acceptors. Taking advantages of the transient nature of dioxetane chemiluminescence, the damage distribution and crack evolution of the hydrogels can be visualized and analyzed with high spatial and temporal resolution. The results demonstrate the strengths of the Ad mechanophore and micellar copolymerization method in the study of damage
evolution and fracture mechanism of swelling hydrogels.

A mechanochemical synthesis of diarylethynes from aryl iodides and calcium carbide as acetylene source is reported. The reaction is catalyzed by a palladium catalyst in the presence of copper salt, base, and ethanol as liquid assisting grinding (LAG) additive. Various aryl and heteroaryl iodides have been converted in up to excellent yields.

Because of the versatility of chiral 1,5-dicarbonyl structural motifs, the development of stereoselective Michael additions of arylacetic acid derivatives to electron-deficient alkenes is an important challenge. Over recent decades, an array of enantio- and diastereoselective methods of this type have been developed through the use of chiral organocatalysts. In this article, three distinct strategies in this research area are highlighted. Catalytic generation of either a chiral iminium electrophile (iminium catalysis) or a chiral enolate nucleophile (Lewis­ base catalysis) has allowed the efficient construction of stereogenic C–C bonds. We also introduce a synergistic catalytic approach involving the merger of these two catalytic cycles that provides selective access to all four stereoisomers of products with vicinal stereocenters.1 Introduction2 Iminium Catalysis3 Lewis Base Catalysis4 Synergistic Organocatalysis5 Summary

A copper-catalyzed, three-component, one-pot, 1,3-dipole cycloaddition/oxidation has been developed to construct pyrrolo[2,1-a]isoquinolinoquinone derivatives, with environmentally friendly oxygen as the oxidant. The pyrrolo[2,1-a]isoquinolinoquinone products were obtained from naturally available tetrahydroisoquinolines, 1,4-naphthoquinones, and benzaldehydes in medium yields.

The synthesis of 1,3-selenazoles and related compounds, including 2,4,5-trisubstituted, 2,4-disubstituted, 4,5-disubstituted, 4-substituted 1,3-selenazoles, and parent unsubstituted 1,3-selenazole, is highlighted. Emphasis is also given on 2-benzoyl-1,3-selenazoles which can be functionalized by Knoevenagel reactions or by rearrangements via their corresponding oximes. Syntheses of bis-, tris-, and tetrakis(1,3-selenazoles) are discussed as well. 1,3,4-6H-Selenadiazines are available from selenosemicarbazides and can undergo ring-contraction or deselenation reactions. Most syntheses rely on the application of selenocarboxylic amides, selenourea and related building blocks which are conveniently available by reaction of the corresponding oxygen analogues with P4Se10.1 Introduction2 Selenocarboxylic Amides3 2,4,5-Tri- and 2,4-Disubstituted 1,3-Selenazoles4 Bis(1,3-selenazoles)5 2-Amino-1,3-selenazoles6 2-Unsubstituted 1,3-Selenazoles7 1,3,4-Selenadiazines8 Conclusions

The exciting field of polymer mechanochemistry has made great empirical progress in discovering reactions in which a stretching force accelerates scission of strained bonds using single molecule force spectroscopy and ultrasonication experiments. Understanding why these reactions happen, i.e., the fundamental physical processes that govern coupling of macroscopic motion to chemical reactions, as well as discovering other patterns of mechanochemical reactivity require complementary techniques, which permit a much more detailed characterization of reaction mechanisms and the distribution of force in reacting molecules than are achievable in SMFS or ultrasonication. A molecular force probe allows the specific pattern of molecular strain that is responsible for localized reactions in stretched polymers to be reproduced accurately in non-polymeric substrates using molecular design rather than atomistically intractable collective motions of millions of atoms comprising macroscopic motion. In this review, we highlight the necessary features of a useful molecular force probe and describe their realization in stiff stilbene macrocycles. We describe how studying these macrocycles using classical tools of physical organic chemistry has allowed detailed characterizations of mechanochemical reactivity, explain some of the most unexpected insights enabled by these probes, and speculate how they may guide the next stage of mechanochemistry.

Organic molecules containing the trifluoromethyl (CF3) group play a vital role in pharmaceuticals, agrochemicals, and materials. New trifluoromethylation methods should encompass capabilities to address issues in efficiency, selectivity, and CF3 source all at once. Fluoroform (CF3H), an industrial byproduct, has emerged as an attractive CF3 source. The reaction profile of the [CuCF3] reagent derived from fluo­roform has surpassed its original applications in cross-coupling-type trifluoromethylation. We have discovered a host of unique copper-mediated trifluoromethylation reactions using [CuCF3] from fluoroform, especially under oxidative conditions, to deliver efficient and selective synthesis of trifluoromethylated compounds.1 Introduction2 Construction of C–CF3 Bonds for the Synthesis of Trifluoromethylated Building Blocks2.1 C(sp)–CF3 Bond Formation2.2 C(sp2)–CF3 Bond Formation2.3 C(sp3)–CF3 Bond Formation3 Domino Synthesis of Trifluoromethylated Heterocycles3.1 3-(Trifluoromethyl)indoles3.2 3-(Trifluoromethyl)benzofurans3.3 2-(Trifluoromethyl)indoles4 Trifluoromethylative Difunctionalization of Arynes4.1 Trifluoromethylation–Allylation of Arynes4.2 1,2-Bis(trifluoromethylation) of Arynes5 Pentafluoroethylation of Unactivated Alkenes6 Conclusion

A novel mononuclear ruthenium (Ru) complex bearing a PNNP-type tetradentate ligand is introduced here as a self-photosensitized catalyst for the reduction of carbon dioxide (CO2). When the pre-activation of the Ru complex by reaction with a base was carried out, an induction period of catalyst almost disappeared and the catalyst turnover numbers (TONs) over a reaction time of 144 h reached 307 and 489 for carbon monoxide (CO) and for formic acid (HCO2H), respectively. The complex has a long lifespan as a dual photosensitizer and reduction catalyst, due to the sterically bulky and structurally robust (PNNP)Ru framework. Isotope-labeling experiments under 13CO2 atmosphere indicate that CO and HCO2H were both produced from CO2.