Nitrogenation of Amides via C–C and C–N Bond Cleavage

Amides are among the fundamental chemicals in organic chemistry.Compared to other carbonyl functional groups,the transformation of amide is relatively difficult and remains a challenge.The traditional deconstruction transformations of amides to other functional products are usually limited to twisted or electronically activated amides.Herein,we describe a direct nitrogenation approach to convert amides into nitriles.This chemistry provides a novel amide transformation pathway via both C–C and C–N bond cleavage.Interestingly,the simple,readily available,and inexpensive inorganic salt NaNO2 is successfully employed as a nitrogen source in this organic N-incorporation process.Applications of this study are demonstrated through the latestage modification of drug and natural product derivatives.

Carbene-Catalyzed Asymmetric Ring-Opening Reaction of Biaryl Lactams to Access Axially Chiral Biaryls

Axially chiral biaryls represent the most important class of atropisomers,and they widely exist in natural products and biologically active molecules.They also constitute a unique scaffold for chiral ligands and catalysts in organic synthesis.The development of synthetic methods to obtain such chiral compounds has received widespread attention,among which catalytically atroposelective ring-opening of configurationally labile compounds represents one of the most attractive strategies.Various substrates with strained cyclic structures,such as the renowned Bringmann's lactones,can undergo asymmetric transformation into stable atropisomers.Known advancement primarily relies on metal catalyst combined with well-designed chiral ligands,the approaches utilizing organocatalysis as a critical resolution strategy are notably scarce.In this study,we disclosed a N-heterocyclic carbene(NHC)-catalyzed asymmetric ring-opening reaction of biaryl lactams via direct atroposelective nucleophilic activation.The optimized bulky carbene catalyst ensures that the reaction can proceed under mild conditions,affording the desired product with good to excellent yields and atroposelectivity.

Metal-free synthesis of quinolines by direct condensation of amides with alkynes: revelation of N-aryl nitrilium intermediates by 2D NMR techniques

Employing triflic anhydride/2-fluoropyridine as an activation system, the coupling reactions of secondary N-aryl amides with terminal alkynes yielded substituted quinolines in moderate to excellent yields. The reaction tolerated both electron-donating and electron-withdrawing groups at the benzamide moiety. Electron-rich aryl acetylenes served as excellent coupling partners, and aliphatic terminal alkynes such as cyclopropyl and conjugate vinyl acetylenes could also be used as reaction partners. By means of 2 D NMR techniques(heteronuclear multiple bond correlation(HMBC), heteronuclear single quantum correlation(HSQC)),nitrilium ions were probed as reactive intermediates which are in contrast with that suggested by Movassaghi on the basis of in situ IR monitoring experiments. On the basis of these results, a plausible mechanism for the formation of quinolines was suggested.

Tf_2O-TMDS combination for the direct reductive transformation of secondary amides to aldimines,aldehydes, and/or amines

The direct partial reduction of highly stable secondary amides to more reactive aldimines and aldehydes is a challenging yet highly demanding transformation. In this context, only three methods have been reported. We report herein an improved version of the Charette's method. Our protocol consists of activation of secondary amides with triflic anhydride/2-fluoropyridine,and partial reduction of the resulting intermediates with 1,1,3,3-tetramethyldisiloxane(TMDS), which delivered aldimines or aldehydes upon acidic hydrolysis. Aromatic amides were reduced to the corresponding aldimines in 85%–100% NMR yields,and yields(NMR) from aliphatic amides were 72%–86%. Acidic hydrolysis of the aldimine intermediates afforded, in one-pot,the corresponding aldehydes in 80%–96% yields. A simple protocol was established to isolate labile aldimines in pure form in92%–96% yields. The improved method gave generally higher yields as compared to the known ones, and features the use of cheaper and more atom-economical TMDS as a chemoselective reducing agent. In addition, a convenient extraction protocol has been established to allow the isolation of amines, which constitutes a mild method for the N-deacylation of amides, another highly desirable transformation. The extended method retains the advantages of the original method of Charette in terms of mild conditions, good functional group tolerance, and excellent chemoselectivity.

Synthesis and biological activity of novel N-(3-furan-2-yl-1-phenyl-1H-pyrazol-5-yl) amides derivatives

A series of novel N-（3-furan-2-yl-l-phenyl-lH-pyrazol-5-yl） amides derivatives were designed and synthesized. Their structures were confirmed by 1H NMR, 13C NMR and HRMS. All title compounds were evaluated for their herbicidal and antifungal activities. Preliminary bioassay results indicated that the title compounds showed good to moderate herbicidal activity at 1000 mg/L. Compound 6q presented the best activity against Digitaria sanguinalis （L） Scop., Amaranthus retroflexus L. and Arabidopsis thaliana with an inhibition degree of five. Compound 6d also showed an inhibition degree of five against D. sanguinalis. In addition, at 50 mg/L, most compounds exhibited good in vitro antifungal activity against Sclerotinia sclerotiorum, with compound 6c showing over 90% antifungal activity against S. sclerotiorum and Pellicularia sasakii.

Preparation,Crystal Structure and Fungicidal Activity of N-(5-(benzofuranol-7-oxymethyl)-1,3,4-thiadiazol-2-yl)amide Compounds

A variety of new N-(5-(benzofuranol-7-oxymethyl)-1,3,4-thiadiazol-2-yl)amide compounds(8a-i)were synthesized through four steps from benzofuranol as raw materials.The crystal structure of compound 8a(C17H21N3O3S,Mr=347.43)was measured by X-ray diffraction,which was classified as monoclinic system,Z=4,V=1742.72(8)Å3,Dc=1.324 Mg/m3,F(000)=736,S=1.03,μ=0.21 mm-1,space group P21 with a=9.9177(3),b=8.9519(2),c=19.8679(5)Å,the final R=0.035 and wR=0.105 for 3873 observed reflections(I>2σ(I)).The X-ray structure presented N(3)-H(3)···N(2)and C(6)-H(6)···O(3)intermolecular hydrogen bonds,which acted as an important role in stabilizing the crystal structure.Additionally,preliminary biological assay on compound 8a showed good fungicidal activity in vivo,with the inhibition of 75%against Pseudoperonospora cu-bensis at 200 mg/L.