Electrochemical Trifluoromethylation and Sulfonylation of N-Allylamides: Synthesis of Oxazoline Derivatives.

We report a new method for the synthesis of trifluoromethylated and sulfonylated oxazolines by electrochemical radical cascade cyclizations of N-allylamides with sodium trifluoromethanesulfinate or sulfonylhydrazines. This protocol provides a green and useful strategy to synthesize trifluoromethylated and sulfonylated oxazolines with a broad substrate scope under ambient conditions.

Electrochemical Decarboxylative Silylation of α,ß-Unsaturated Carboxylic Acids.

An electrochemical method for the decarboxylative silylation of α,ß-unsaturated carboxylic acids was developed. A variety of alkenylsilanes could be obtained in satisfactory yields and excellent selectivities under external oxidant- and metal-free conditions. Mechanistic studies showed that the formation of the silyl radical was mediated by NHPI, which produces the hydrogen atom transfer (HAT) reagent phthalimide N-oxyl (PINO) via multiple-site concerted proton-electron transfer (MS-CPET).

Annulation Reaction of Quinoxalin-2(1H)-ones Initiated by Electrochemical Decarboxylation of N-Arylglycines.

A new methodology for the synthesis of tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones has been accomplished through annulation of quinoxalin-2(1H)-ones initiated by electrochemical decarboxylation of N-arylglycines catalyzed by ferrocene. With a pair of oxidative and reductive processes occurring among the substrates and intermediates instead of on the electrodes, the electricity consumption was decreased.

Electrochemically Enabled Sulfoximido-Oxygenation of Alkenes with NH-Sulfoximines and Alcohols.

An electrochemical oxidative sulfoximido-oxygenation of alkenes has been developed by using NH-sulfoximines and alcohols directly. This method proceeds regioselectively without metal catalysts and external chemical oxidants and shows broad substrate scope and diverse functional group compatibility. Based upon the preliminary mechanism studies, N-centered sulfoximidoyl radicals were involved in this electrochemical process.

Electrochemical Oxidative C(sp2)-H Amination of Aldehyde Hydrazones with Azoles.

A general and highly efficient method for the electrochemical C(sp2)-H amination of aldehyde hydrazones with azoles has been developed. This reaction proceeds under exogenous metal-, catalyst-, and oxidant-free conditions to provide aminated hydrazone derivatives in good to excellent yields. This strategy applies to both aromatic and aliphatic aldehyde hydrazones and tolerates a broad range of functional groups.

Electrosynthesis of (hetero)aryl nitriles from α-imino-oxy acids via oxidative decarboxylation/N-O cleavage.

A new method for the synthesis of (hetero)aryl nitriles via iminyl radicals has been developed through the electrochemical oxidative decarboxylation of α-imino-oxy acids. This protocol provides an efficient approach to nitriles with a broad range of functional-group tolerance under ambient conditions and can be applied for one-pot gram-scale synthesis.

Hydropyridylation of α,ß-Unsaturated Esters through Electroreduction of 4-Cyanopyridine.

A mild and highly efficient method for the hydropyridylation of α,ß-unsaturated esters has been developed. This protocol provides the products smoothly with a wide substrate scope in an undivided cell under ambient conditions. Moreover, studies showed that the scope could be extended to other unsaturated compounds, including enones and aldehydes.

Iminyl-radicals by electrochemical decarboxylation of α-imino-oxy acids: construction of indole-fused polycyclics.

Iminyl radicals are reactive intermediates that can be used for the construction of various valuable heterocycles. Herein, the electrochemical decarboxylation of α-imino-oxy acids for the generation of iminyl radicals has been accomplished under exogenous-oxidant- and metal-free conditions through the use of nBu4NBr as a mediator. The resulting iminyl radicals undergo intramolecular cyclization smoothly with the adjacent (hetero)arenes to afford a series of indole-fused polycyclic compounds.

Double ryanodine receptor mutations confer higher diamide resistance in rice stem borer, Chilo suppressalis.

BACKGROUND: The striped rice stem borer, Chilo suppressalis (Lepidoptera: Pyraidae), is one of the most serious rice pests in China. Chlorantraniliprole was used extensively for C. suppressalis control over the past ten years, and some field populations have developed high resistance. In this study, we report the chlorantraniliprole resistance status of C. suppressalis in China and the resistance mechanism. RESULTS: Significant geographical variations of chlorantraniliprole susceptibility were observed among 28 C. suppressalis field populations in 2019-2020. The LC50 values varied from 2907.874 mg L-1 (XS19) to 1.524 mg L-1 (QW19). Most tested field populations collected from Zhejiang, Jiangxi, Hunan and Anhui provinces in 2020 showed a high level of resistance to chlorantraniliprole (RR = 311.9-2060.1), whereas Jiangsu and Sichuan province populations remained susceptible. Analysis of RyR mutations showed that mutations of I4758M, Y4667D, Y4667C and Y4891F were present in resistant populations of C. suppressalis with different levels of chlorantraniliprole resistance. The frequency of the Y4667C mutation was correlated with chlorantraniliprole resistance in YY19 (RR = 702.6) and YY20 (RR = 1426.8) populations, with the homozygous mutation frequencies of 15.6% and 29.4%, respectively. High contributions of the I4758M and Y4667C double mutation to diamide resistance was demonstrated with CRISPR/Cas9-modified D. melanogaster. Flies bearing the Y4667C mutation (I4758M and Y4667C double mutation in C. suppressalis) exhibited high resistance to chlorantraniliprole (RR = 172.1), and moderate resistance to cyantraniliprole (RR = 79.2) and tetra chlorantraniliprole (RR = 43.6), which were higher than that of single mutations. CONCLUSIONS: Chlorantraniliprole resistance in C. suppressalis is intensifying in China. RyR double mutations (i.e. I4758M and Y4667C) confer higher diamide resistance than single mutations.

Monitoring and mechanisms of insecticide resistance in Spodoptera exigua (Lepidoptera: Noctuidae), with special reference to diamides.

The beet armyworm, Spodoptera exigua, is a major lepidopteran pest of global importance in cultivation of numerous crops including cotton, maize, soybean, onion, cabbage, and ornamentals. It has evolved resistance to different insecticides. However, the current status of insecticide resistance in S. exigua has not been well examined in China. In this study, concentration-mortality responses of S. exigua to seven insecticides, including chlorantraniliprole, tetraniliprole, methoxyfenozide, indoxacarb, chlorfenapyr, emamectin benzoate and beta-cypermethrin were evaluated. The results showed that most of the tested populations had developed moderate to high resistance to chlorantraniliprole, with resistance ratios ranging from 6.3 to 2477.3-fold. Our results also showed that chlorantraniliprole have cross-resistance with tetraniliprole in S. exigua. The AY19 population collected from Anyang in Henan Province in 2019 exhibited a high resistance level to beta-cypermethrin (RR = 277.5). Methoxyfenozide and chlorfenapyr were highly effective against all of the tested populations with resistance ratios (RR) ranging from 0.1 to 2.2-fold. One of the tested populations showed moderate resistance to indoxacarb and emamectin benzoate. We detected the known ryanodine receptor target site resistance mutation, I4743M, in the field populations of S. exigua with different levels of diamide resistance.

Susceptibility of fall armyworm, Spodoptera frugiperda (J.E.Smmith), to eight insecticides in China, with special reference to lambda-cyhalothrin.

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is the main destructive insect pest of grain crops that occurs in all maize growing regions of the Americas. It has rapidly invaded the Southern China since January 2019. However, the current status of insecticide resistance in S. frugiperda has not been reported in China. In this study, we determined the susceptibility of eight populations of FAW to eight insecticides by an artificial diet incorporation method. The results showed that among eight insecticides, emamectin benzoate, spinetoram, chlorantraniliprole, chlorfenapyr, and lufenuron showed higher toxicity to this pest, while lambda-cyhalothrin and azadirachtin exhibited lower toxicity. Susceptibility of S. frugiperda to indoxacarb was significantly different (10.0-fold for LC50) across the various geographic populations. To investigate the biochemical mechanism of FAW to lambda-cyhalothrin, we performed the synergism tests and the results showed that piperonyl butoxide (PBO) and triphenyl phosphate (TPP) produced a high synergism of lambda-cyhalothrin effects in the two field populations. Sequencing of the gene encoding the acetylcholinesterase (AChE) gene in the two field populations identified two amino acid mutations, all of which have been shown previously to confer resistance to organophosphates (OPs) in several arthropod species. The results of this study provided valuable information for choosing alternative insecticides and for insecticide resistance management of S. frugiperda.

Venom serine proteinase homolog of the ectoparasitoid Scleroderma guani impairs host phenoloxidase cascade.

The ant-like bethylid ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) envenomates host to suppress immune response. Yet, the roles of its venom in inhibiting melanization of the host hemolymph have not been fully characterized. Here, we demonstrated that S. guani envenomation induced strong inhibition of melanization of the hemolymph from Tenebrio molitor (Coleoptera: Tenebrionidae), permitting the successful development of parasitoid offspring. To reveal venom component associated with such function, a serine proteinase homolog (SguaSPH) rich in the venom of S. guani was characterized. It was found that one of the catalytic triad residues for serine proteinase is absent in the amino acid sequence of SguaSPH. This venom component was abundantly expressed in venom apparatus and adult stages. By enzymatic assays, SguaSPH displayed low trypsin and no chymotrypsin activity, and was able to inhibit phenoloxidase activity in the hemolymph of Ostrinia furnacalis (Lepidoptera: Crambidae). The findings suggest that SguaSPH is essential for interfering with hemolymph melanization of S. guani envenomated host via phenoloxidase cascade disruption.

The synthesis of sulfonated 4H-3,1-benzoxazines via an electro-chemical radical cascade cyclization.

A new route for the synthesis of sulfonated 4H-3,1-benzoxazines has been accomplished by electrochemical radical cascade cyclizations of styrenyl amides with sulfonylhydrazines. This process demonstrates a wide substrate scope with diverse functional group compatibility under metal- and external oxidant-free conditions at ambient temperature.

Synthesis of 3-Formylindoles via Electrochemical Decarboxylation of Glyoxylic Acid with an Amine as a Dual Function Organocatalyst.

A new method for 3-formalytion of indoles has been developed through electrochemical decarboxylation of glyoxylic acid with the amine as a dual function organocatalyst. The amine facilitated both the electrochemical decarboxylation and the nucleophilic reaction efficiently, whose loading can be as low as 1 mol %. This protocol has a broad range of functional group tolerance under ambient conditions. The gram-scale experiment has shown great potential in the synthetic application of this strategy.

Electrosynthesis of ( E)-Vinyl Thiocyanates from Cinnamic Acids via Decarboxylative Coupling Reaction.

Thiocyanate compounds are key intermediates in the synthesis of pharmaceuticals and other sulfur-containing organic compounds. Herein, we first report an electrochemical protocol to synthesize vinyl thiocyanates from decarboxylative coupling of cinnamic acids with NH4SCN in aqueous solution. This method provides thiocyanation products with broad functional group tolerance under ambient conditions.

Stereoselective synthesis of sulfur-containing ß-enaminonitrile derivatives through electrochemical Csp3-H bond oxidative functionalization of acetonitrile.

Incorporation of nitrile groups into fine chemicals is of particular interest through C(sp3)-H bonds activation of alkyl nitriles in the synthetic chemistry due to the highly efficient atom economy. However, the direct α-functionalization of alkyl nitriles is usually limited to its enolate chemistry. Here we report an electro-oxidative C(sp3)-H bond functionalization of acetonitrile with aromatic/aliphatic mercaptans for the synthesis of sulfur-containing ß-enaminonitrile derivatives. These tetrasubstituted olefin products are stereoselectively synthesized and the stereoselectivity is enhanced in the presence of a phosphine oxide catalyst. With iodide as a redox catalyst, activation of C(sp3)-H bond to produce cyanomethyl radicals proceeds smoothly at a decreased anodic potential, and thus highly chemoselective formation of C-S bonds and enamines is achieved. Importantly, the process is carried out at ambient temperature and can be easily scaled up.

Molecular features and expression profiles of octopamine receptors in the brown planthopper, Nilaparvata lugens.

BACKGROUND: Octopamine, the invertebrate counterpart of adrenaline and noradrenaline, regulates and modulates many physiological and behavioral processes in insects. It mediates its effects by binding to specific octopamine receptors, which belong to the superfamily of G-protein coupled receptors (GPCRs). The expression profiles of octopamine receptor genes have been well documented in different developmental stages and multiple tissue types in several different insect orders. However, little work has addressed this issue in Hemiptera. RESULTS: In this study, we cloned four octopamine receptor genes from brown planthopper. The deduced amino acid sequences share high identity with other insect homologues and have the characteristic GPCRs domain architecture: seven transmembrane domains. These genes were expressed in all developmental stages and examined tissues. The expression of NlOA2B3 and NlOA3 was relatively higher in egg and first instar nymph stage than in other stages and other receptor genes. All of these receptor genes were more highly expressed in brain than other tissues. CONCLUSION: The identification of octopamine receptor genes in this study will provide a foundation for investigating the diverse roles played by NlOARs and for exploring specific target sites for chemicals that control agricultural pests. © 2019 Society of Chemical Industry.

Superoxide dismutase from venom of the ectoparasitoid Scleroderma guani inhibits melanization of hemolymph.

Superoxide dismutase (SOD) known as an important antioxidative stress protein has been recently found in venoms of several parasitoid wasps. However, its functions and characteristics as a virulent factor remain scarcely described. Here, we report the characterization of two venomous SOD genes (SguaSOD1 and SguaSOD3) from the ectoparasitoid, Scleroderma guani. The metal binding sites, cysteine amino acid positions and signature sequences of the SOD family were conserved within SguaSOD1 and SguaSOD3. Relatively high levels of their transcripts were observed in pupae followed a decrease in early adults, after which they had the highest transcriptions, indicating that their productions would be regulated in venom apparatus. Although the two genes showed lower expression in venom apparatus compared to head and thorax, the enzymatic assay revealed that SOD indeed had activity in venom. Further, we showed that recombinant SguaSOD3 suppressed melanization of host hemolymph, implying that this protein used as a virulent factor uniquely impacts the prophenoloxidase cascade.

Electrochemical Synthesis of Bisindolylmethanes from Indoles and Ethers.

An electrochemical bisindolylation of ethers was developed. Carried out under ambient conditions and in the absence of any chemical oxidants, this reaction exhibits a broad substrate scope and good functional group compatibility.

Molecular characterization and expression profiling of ryanodine receptor gene in the pink stem borer, Sesamia inferens (Walker).

The susceptibilities of three field populations of pink stem borer (PSB), Sesamia inferens (walker) to diamide insecticides, chlorantraniliprole and flubendiamide, were evaluated in this study. The results showed that these PSB field populations were still sensitive to the two diamide insecticides after many years of exposure. To further understand PSB and diamide insecticide, the full-length ryanodine receptor (RyR) cDNA (named as SiRyR), the molecular target of diamide insecticides was cloned from PSB and characterized. The SiRyR gene contains an open reading frame of 15,420 nucleotides, encoding 5140 amino acid residues, which shares 77% to 98% sequence identity with RyR homologous of other insects. All hallmarks of RyR proteins are conserved in the SiRyR protein, including the conserved C-terminal domain with the consensus calcium-biding EF-hands (calcium-binding motif), the six transmembrane domains, as well as mannosyltransferase, IP3R and RyR (pfam02815) (MIR) domains. Real-time qPCR analysis revealed that the highest mRNA expression levels of SiRyR were observed in pupa and adults, especially in males. SiRyR was expressed at the highest level in thorax, and the lowest level in wing. The full genetic characterization of SiRyR could provide useful information for future functional expression studies and for discovery of new insecticides with selective insecticidal activity.