Catalytic Asymmetric Cascade Dearomatization of Indoles via a Photoinduced Pd-Catalyzed 1,2-Bisfunctionalization of Butadienes.

Photoinduced Pd-catalyzed bisfunctionalization of butadienes with a readily available organic halide and a nucleophile represents an emerging and attractive method to assemble versatile alkenes bearing various functional groups at the allylic position. However, enantiocontrol and/or diastereocontrol in the C-C or C-X bond-formation step have not been solved due to the open-shell process. Herein, we present a cascade asymmetric dearomatization reaction of indoles via photoexcited Pd-catalyzed 1,2-biscarbonfunctionalization of 1,3-butadienes, wherein asymmetric control on both the nucleophile and electrophile part is achieved for the first time in photoinduced bisfunctionalization of butadienes. This method delivers structurally novel chiral spiroindolenines bearing two contiguous stereogenic centers with high diastereomeric ratios (up to >20 : 1 dr) and good to excellent enantiomeric ratios (up to 97 : 3 er). Experimental and computational studies of the mechanism have confirmed a radical pathway involving excited-state palladium catalysis. The alignment and non-covalent interactions between the substrate and the catalyst were found to be essential for stereocontrol.

Asymmetric Hydrogenation of Racemic 2-Substituted Indoles via Dynamic Kinetic Resolution: An Easy Access to Chiral Indolines Bearing Vicinal Stereogenic Centers.

The asymmetric hydrogenation (AH) of N-unprotected indoles is a straightforward, yet challenging method to access biologically interesting NH chiral indolines. This method has for years been limited to 2/3-monosubstituted or 2,3-disubstituted indoles, which produce chiral indolines bearing endocyclic chiral centers. Herein, we have reported an innovative Pd-catalyzed AH of racemic α-alkyl or aryl-substituted indole-2-acetates using an acid-assisted dynamic kinetic resolution (DKR) process, affording a range of structurally fascinating chiral indolines that contain exocyclic stereocenters with excellent yields, diastereoselectivities, and enantioselectivities. Mechanistic studies support that the DKR process relies on a rapid interconversion of each enantiomer of racemic substrates, leveraged by an acid-promoted isomerization between the aromatic indole and nonaromatic exocyclic enamine intermediate. The reaction can be performed on a gram scale, and the products can be derivatized into non-natural ß-amino acids via facile debenzylation and amino alcohol upon reduction.

The Effect of Botanical Pesticides Azadirachtin, Celangulin, and Veratramine Exposure on an Invertebrate Species Solenopsis invicta (Hymenoptera: Formicidae).

The injudicious and excessive use of synthetic pesticides has deleterious effects on humans, ecosystems, and biodiversity. As an alternative to traditional crop-protection methods, botanical pesticides are gaining importance. In this research endeavor, we examined the contact toxicity, knockdown time, lethal time, and toxicity horizontal transmission of three natural pesticides from plants (azadirachtin, celangulin, and veratramine) on red imported fire ants (RIFA; Solenopsis invicta). Our research findings indicated that azadirachtin and celangulin exhibited relatively high toxicity, with median lethal dose (LD50) values of 0.200 and 0.046 ng/ant, respectively, whereas veratramine exhibited an LD50 value of 544.610 ng/ant for large workers of S. invicta at 24 h post-treatment. Upon treatment with 0.125 mg/L, the (median lethal time) LT50 values of azadirachtin and celangulin were determined to be 60.410 and 9.905 h, respectively. For veratramine, an LT50 value of 46.967 h was achieved after being tested with 200 mg/L. Remarkably, azadirachtin and celangulin were found to exhibit high horizontal transfer among RIFA, with high secondary mortality (100%) and tertiary mortalities (>61%) after 48 h of treatment with 250 mg/L, as well as with their dust formulations for 72 h. However, veratramine did not exhibit significant toxicity or horizontal transfer effects on RIFA, even at high concentrations. These findings suggest that azadirachtin and celangulin are likely to have a highly prominent potential in the management of S. invicta.

Efficacy of Matrine, Rotenone, and Pyrethrin Against Red Imported Fire Ant Solenopsis invicta (Hymenoptera: Formicidae) and Their Impact on Aquatic Organisms.

Chemicals, including toxic bait and dusts, are the main means of controlling the red imported fire ant Solenopsis invicta (abbreviation 'RIFA'), which is a serious invasive pest. To identify environmentally friendly chemicals for controlling RIFA, we tested the toxicity and horizontal transfer of three botanical insecticides-matrine, rotenone, and pyrethrin-and their impact on aquatic organisms (i.e., three fish and one shrimp). The LD50 value of matrine, rotenone, and pyrethrin was 0.24, 50.929, and 13.590 ng/ant, respectively. Matrine, rotenone, and pyrethrin had effective horizontal transfer and caused significant secondary mortality. After exposure to donor workers, 90.75%, 90.75%, and 100% of recipient workers in the 0.025% matrine, 1.0% rotenone, and 0.3% pyrethrin dust treatments, respectively, died within 48 h. Furthermore, 0.025% matrine dust caused significant tertiary mortality (49.5%). Tertiary mortality caused by 1.0% rotenone and 0.3% pyrethrin dusts was very low, only 7.75% and 18.5%, respectively. In a field trial, the comprehensive mortality effect of 0.05% matrine, 1.50% rotenone, and 0.375% pyrethrin dust was 74.96%, 30.10%, and 29.27%, respectively, after 14 d of treatment. Matrine had low toxicity to the fish Hypophthalmichthys molitrix, and 37.5 mg/L pyrethrin had low toxicity to the fish Cirrhinus molitorella, H. molitrix, and Oreochromis niloticus. However, rotenone was highly toxic to all three fish. The shrimp Neocaridina denticulate was not sensitive to matrine, rotenone, or pyrethrin. Matrine dust has highly effective horizontal transfer, and 0.05% matrine dust has great potential for managing RIFA in organic farms, aquaculture farms of H. molitrix, and water resource regions.