MarjoW

Synthesis
DOI: 10.1055/s-0040-1719842

We report the palladium-catalyzed, dearomative syn-1,2-diamination of the non-activated arenes benzene and naphthalene using aryl isocyanates. This reaction proceeds with exclusive syn-1,2-selectivity and provides a complementary regio- and stereoselectivity to previously described arenophile-based transformations. The products are amenable to further synthetic elaboration, including selective diene functionalization and heterocycle cleavage. Overall, this dearomatization provides synthetic access to unprecedented saturated nitrogen-containing heterocyclic motifs and syn-1,2-diaminated cyclohexane products.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Synlett
DOI: 10.1055/s-0040-1720889

Under thermal conditions, 1,4,2-dioxazol-5-ones are known to undergo decarboxylation followed by Lossen’s rearrangement to yield isocyanates. Described herein is the in situ trapping of the resulting isocyanates with carbon nucleophiles to synthesize β-keto amides. Furthermore, a general and mild method for the conversion of the resulting β-keto amides into quinolin-2-ones is reported.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Synthesis
DOI: 10.1055/a-1582-0169

P-Stereogenic secondary phosphine oxides [SPOs, RR′P(O)H], valuable ligands for metal complexes in asymmetric catalysis, are also building blocks for other chiral phosphorus derivatives. This short review summarizes methods used for asymmetric synthesis of P-stereogenic SPOs.1 Introduction2 Configurational Stability of P-Stereogenic SPOs3 Classical Resolution, HPLC Separation, and Dynamic Resolution4 Synthesis via Chiral Auxiliaries5 Kinetic Resolution6 Conclusions and Outlook
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Abstract

C-methylation is a vitally important reaction applicable in chemical synthesis and structure-based drug design. Notably, the “magic methyl” effect has become decisive in medicinal chemistry and drug discovery for the modulation of bio-active properties in life science molecules. In this regard, C-methylation reaction is widely applied chemical modification in various biomolecules, pharmaceuticals, and natural products. In general, this reaction often relies on activated, hazardous and uneconomical methyl sources such as diazomethane, dimethyl sulfate, and methyl halides. To achieve methylation reactions in a sustainable and cost-effective manner, the use of ‘ideal’ C1 source is crucial. In this regard, methanol constitutes an expedient −CH₃ source because this simple alcohol is less-hazardous, inexpensive, and abundantly available platform chemical as well as it produces only water as the by-product in methylation processes. Regarding potential catalysts to perform C-methylation using methanol by hydrogen borrowing methodology, non-noble metal-based catalysts are highly preferable due to their unique advantages such as more abundance, inexpensive and low-toxicity. In recent years, chemists made significant contributions towards catalytic valorization of methanol as C1 source to insert methyl groups via C−H activation in a variety of compounds and life science molecules. Consequently, in this minireview we summarize the C-methylation process using methanol by applying Fe-, Mn-, Co- and Ni-based catalysts as well as metal free catalysts.

Abstract

Lignin valorization allows the generation of a number of value-added products such as cis,cis-muconic acid (ccMA), which is widely used for the synthesis of chemicals for the production of biodegradable plastic materials. In the present work, we reported the first multi-enzymatic, one-pot bioconversion process of vanillin into ccMA. In details, we used four sequential reactions catalyzed by xanthine oxidase, O-demethylase LigM (and the tetrahydrofolate-regeneration enzyme methyl transferase MetE), decarboxylase AroY (based on the use of E. coli transformed cells) and catechol 1,2-dioxygenase CatA. The optimized lab-scale procedure allowed to reach, for the first time, the conversion of 5 mM vanillin into ccMA in ∼30 h with a 90% yield: this achievement represents an improvement in terms of yields and time when compared to the use of a whole-cell system. This multi-enzymatic system represents a sustainable alternative for the production of a high value added product from a renewable resource.

Synlett
DOI: 10.1055/s-0040-1720887

Self-assembled aggregates of 7,10-dibromo-2,3-dicyanopyrazinophenanthrene which act as a new organophotocatalyst in combination with Ni catalyst for the Caryl–Oacyl cross-coupling reactions of carboxylic acids with aryl halides are described. This visible-light-induced Caryl–Oacyl bond-formation reaction proceeds smoothly to afford aryl esters with satisfactory to excellent yields.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
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