Photoinduced Electron Transfer from Xanthates to Acyl Azoliums: Divergent Ketone Synthesis via N-Heterocyclic Carbene Catalysis.

Considering the prevalence of alcohols and carboxylic acids, their fragment cross-coupling reactions could hold significant implications in organic synthesis. Herein, we report a versatile method for synthesizing a diverse range of ketones from alcohols and carboxylic acid derivatives via N-heterocyclic carbene (NHC) catalysis. Mechanistic investigations revealed that photoexcited xanthates and acyl azoliums undergo single electron transfer (SET) under photocatalyst-free conditions, generating NHC-derived ketyl radicals and alkyl radicals. These open-shell intermediates subsequently undergo the radical-radical cross-coupling reaction, yielding valuable ketones. Furthermore, this approach can be employed in three-component reactions involving alkenes and enynes, resulting in structurally diverse cross-coupled ketones. The unified strategy offers a unique opportunity for the fragment coupling of a diverse range of alcohols and carboxylic acid derivatives, accommodating diverse functional groups even in complex settings.

Site-Selective Pyridine C-H Alkylation with Alcohols and Thiols via Single-Electron Transfer of Frustrated Lewis Pairs.

A unified strategy for the deoxygenative or desulfurative pyridylation of various alcohols and thiols has been developed through a single-electron transfer (SET) process of frustrated Lewis pairs (FLPs) derived from pyridinium salts and PtBu3 . Mechanistic studies revealed that N-amidopyridinium salts serve as effective Lewis acids for the formation of FLPs with PtBu3 , and the generated phosphine radical cation ionically couples with the in situ generated xanthate, eventually affording the alkyl radical through facile ß-scission under photocatalyst-free conditions. The reaction efficiency was further accelerated by visible-light irradiation. This method is conceptually appealing by using encounter complexes in FLP chemistry to promote SET, which provides a previously unrecognized opportunity for the selective heteroarylation of a diverse range of alcohols and thiols with various functional groups, even in complex settings under mild reaction conditions.

Asymmetric Organocatalytic [4 + 1] Annulations Involving a Polarity Reversal Process: A Tandem Catalytic Approach to Highly Functionalized Spiropyrazolone Derivatives.

A tandem catalytic strategy for the asymmetric synthesis of spirocyclopentanone pyrazolones bearing three contiguous stereocenters and two quaternary carbons with good stereoselectivities has been developed. This strategy, using pyrazolones as efficient C1 synthons and involving a polarity reversal process, not only overcame the energy barrier of the dearomatization process but also avoided nucleophilic addition of the hydroxy group in the enol form tautomer. Futhermore, spirocyclopentanones could be transformed into spirocyclohexamide pyrazolone with the Lawesson reagent.

One-Pot Asymmetric Synthesis of Spiropyrazolone-Linked Cyclopropanes and Benzofurans through a General Michael Addition/Chlorination/Nucleophilic Substitution Sequence.

A sequential and general strategy has been successfully developed for the synthesis of spiropyrazolone scaffolds. This intriguing transformation of the asymmetric multicomponent catalysis process was realized with the combination of Michael addition/chlorination/nucleophilic substitution in a one-pot sequence, giving rise to a series of spiropyrazolones with fully substituted cyclopropanes and spiro-dihydrobenzofurans containing continuous stereogenic centers in good yields with excellent stereoselectivities.

Participation of ß-Ketothioamides in N-Heterocyclic Carbene-Catalyzed [3 + 3] Spiroannulation: Asymmetric Synthesis of Functionalized Spiro-piperidinone Derivatives.

An N-heterocyclic carbene-catalyzed asymmetric [3 + 3] spiroannulation of ß-ketothioamide was successfully developed. ß-Ketothioamides exhibit an unusual reactivity to undergo a previously challenging lactamization reaction, and the desired spiro-piperidinone derivatives containing two vicinal stereogenic centers were synthesized in good to high yields with high stereoselectivities, whose structure can be converted to the corresponding imide and δ-lactam derivatives smoothly.

Harnessing the potential of acyl triazoles in bifunctional cobalt-catalyzed radical cross-coupling reactions.

Persistent radicals facilitate numerous selective radical coupling reactions. Here, we have identified acyl triazole as a new and versatile moiety for generating persistent radical intermediates through single-electron transfer processes. The efficient generation of these persistent radicals is facilitated by the formation of substrate-coordinated cobalt complexes, which subsequently engage in radical cross-coupling reactions. Remarkably, triazole-coordinated cobalt complexes exhibit metal-hydride hydrogen atom transfer (MHAT) capabilities with alkenes, enabling the efficient synthesis of diverse ketone products without the need for external ligands. By leveraging the persistent radical effect, this catalytic approach also allows for the development of other radical cross-coupling reactions with two representative radical precursors. The discovery of acyl triazoles as effective substrates for generating persistent radicals and as ligands for cobalt catalysis, combined with the bifunctional nature of the cobalt catalytic system, opens up new avenues for the design and development of efficient and sustainable organic transformations.

One-Pot Enantioselective Construction of Polycyclic Tetrahydroquinoline Scaffolds through Asymmetric Organo/Photoredox Catalysis via Triple-Reaction Sequence.

A novel one-pot triple-reaction strategy for the asymmetric construction of polycyclic skeletons with multiple consecutive chiral centers through aza-Michael/Michael/Wittig/ketyl radical addition/esterification processes is reported. A wide range of polycyclic tetrahydroquinoline derivatives were smoothly obtained from easily available starting materials with good results (up to 80% yield, >20:1 dr, >99% ee) under mild conditions. In this transformation, five chemical bonds and five consecutive chiral centers were successively formed.

[Strengthening the effect of Bacillus megaterium on remediation of Cd-contaminated farmland soil by Sedum plumbizincicola]. / 巨大芽孢杆菌对伴矿景天修复镉污染农田土壤的强化作用.

Sedum plumbizincicola is a Cd and Zn hyperaccumulator, widely used for the phytoremediation of Cd-contaminated soil. Bacillus megaterium, a phosphate-solubilizing bacteria, can promote plant growth and improve the bioavailability of heavy metals in soil, and thus has a strengthening effect on the remediation of heavy metal-contaminated soil. Here, a pot experiment was carried out with S. plumbizincicola as a hyperaccumulator to investigate the effects of different inoculation amounts (10-60 mL) of B. megaterium on the phytoremediation efficiency of Cd-contaminated farmland soils. The results showed that inoculation of B. megaterium increased soil available Cd content by 15.0%-45.0% compared with the CK. Biomass of shoots and roots of S. plumbizincicola increased by 8.7%-66.7% and 13.6%-81.8%, respectively. Shoot Cd concentration was significantly increased by the application of B. megaterium by 29.2%-60.4%. Under the conditions of S. plumbizincicola inoculated with B. megaterium, Cd removal rate of soil reached 26.7%-42.9%. In conclusion, application of B. megaterium in phytoremediation significantly enhanced the Cd removal efficiency and increased plant biomass, which promoted Cd remediation efficiency.

[Cadmium accumulation and its development tendency in black soil under long-term fertilization].

Based on the long-term field experiment at Hailun Agro-ecosystem Experimental Station of Chinese Academy of Sciences, this paper studied the cadmium (Cd) accumulation, its development tendency, and Cd availability in black soil under effects of long-term application of chemical N and P fertilizers and pig manure. The results showed that under no fertilization, soil Cd concentration had a slight increase. Long-term chemical N and P fertilization increased soil Cd concentration significantly, but soil Cd accumulation had less difference under different N and P fertilization rates. Applying pig manure increased the Cd accumulation in soil significantly, and the accumulation had a tendency of speed-up. Cd-containing feedstuff additives could be the important source of Cd in pig manure. No significant effects of chemical N and P fertilization were observed on the Cd availability in soil, but long-term application of pig manure increased the Cd availability significantly.