Pd-catalyzed carbonylation of diazo compounds at atmospheric pressure: a catalytic approach to ketenes

The carbonylation of carbenes through catalytic cycles is highly desirable due to the importance of ketene-mediated reactions in organic synthesis. In this investigation, a highly efficient and mild catalytic approach toward ketene intermediates has been developed based on Pd-catalyzed carbonylation of diazo compounds with CO. When α-diazocarbonyl compounds or N-tosylhydrazone salts are heated in the presence of a palladium catalyst under atmospheric pressure of CO, ketene intermediates are formed in situ, where they undergo further reactions with various nucleophiles such as alcohols, amines, or imines. The Pd-catalyzed tandem carbonylation-Staudinger cycloaddition gives β-lactam derivatives in good yields with excellent trans diastereoselectivity. The results from DFT calculation on the reaction mechanism suggest that Pd is involved in the [2 + 2] cycloaddition process and affects the diastereoselectivity of the β-lactam products by assisting isomerization of the addition intermediate. On the other hand, the acylketenes generated from the Pd-catalyzed carbonylation of α-diazoketones react with imines in a formal [4 + 2] cycloaddition manner to afford 1,3-dioxin-4-one derivatives. This straightforward carbonylation provides a new approach toward highly efficient catalytic generation of ketene species under mild conditions.     

Difference in moments of inertia and paring interaction strength in superdeformed nuclei

The difference in the bandhead moments of inertia between the superdeformed (SD) band¹⁹⁴Hg(1) and the two-quasiparticle SD bands¹⁹⁴Hg(2, 3) was investigated using the particle-number-conserving treatment for the cranked shell model Hamiltonian. and the pairing interaction strength in SD nuclei is estimated to be much weaker than that in normally deformed nuclei.     

DSA、CTA联合MR影像评估AIS患者脑支循环及预后性关系

探讨数字减影血管成像(DSA)、计算机断层扫描血管成像(CTA)联合磁共振(MR)影像评估急性缺血性卒中(AIS)患者脑支循环及预后性关系。选取60例大脑中动脉M1段急性闭塞所致AIS患者为研究对象,根据DSA、CTA与MR影像对其脑侧支循环评估,比较患者基线资料、结局指标等,并分析预后性。结果发现:基于DSA、CTA与MR影像对AIS患者脑侧支循环评估结果一致性良好;3种影像模式下脑侧支循环良好组与不良组结局资料差异显著(P<0.05);多因素分析显示,FVH-ASPECTS评分、rLMC评分、ASITN/SIR分级量表均为AIS患者神经功能预后的独立影响因素。总之,DSA、CTA、MR影像对AIS患者脑侧支循环评估具有一致性,且FVH-ASPECTS评分、rLMC评分、ASITN/SIR分级量表均为AIS患者神经功能预后的独立影响因素。     

Catalytic Asymmetric Bromination of Unfunctionalized Olefins with H2O as a Nucleophile

The dimeric cinchona alkaloid (DHQD)₂PHAL is used to catalyze an effective asymmetric bromohydroxylation of unfunctionalized olefins with H₂O as nucleophile an N‐bromobenzamide as a bromine source. A variety of optically active bromohydrins are formed with up to 88 % ee.     

Cu(I)-catalyzed asymmetric diamination of conjugated dienes

A Cu(I)-catalyzed asymmetric diamination for a variety of conjugated dienes and a triene with encouraging ee's has been effectively achieved using (R)-DTBM-SEGPHOS as a chiral ligand and di- tert-butyldiaziridinone as the nitrogen source.     

Catalytic asymmetric allylic and homoallylic diamination of terminal olefins via formal C-H activation

This paper describes a catalytic asymmetric diamination process for terminal olefins at allylic and homoallylic carbons via formal C-H activation using di-tert-butyldiaziridinone as nitrogen source with a catalyst generated from Pd2(dba)3 and chiral phosphorus amidite ligand. A wide variety of readily available terminal olefins can be effectively diaminated in good yields with high regio-, diastereo-, and enantioselectivities.     

pH Responsive Poly(Amino Acid) Nanoparticles as Potent Carrier Adjuvants for Enhancing Cellular Immunity

Adjuvants are widely used in vaccine to improve the protection or treatment efficacy. However, so far they inevitably produce side effects and are hard to induce cellular immunity in practical application. Herein, two kinds of amphiphilic poly(glutamic acid) nanoparticles (α-PGA-F and γ-PGA-F NPs) as nanocarrier adjuvants are fabricated to induce an effective cellular immune response. Amphiphilic PGA are synthesized by grafting phenylalanine ethyl ester to form biodegradable self-assembly nanoadjuvants in a water solution. The model antigen, chicken ovalbumin (OVA), can be loaded into PGA-F NPs (OVA@PGA-F NPs) with the high loading ratio >12%. Moreover, compared with γ-PGA-F NPs, the acidic environment can induce the α-helical secondary structure of α-PGA NPs, promoting membrane fusion and more fast antigen lysosomal escape. Hence, the antigen presenting cells treated with OVA@α-PGA-F NPs show higher secretion of inflammatory cytokines, and higher expression of major biological histocompatibility complex class I and CD80 than those of OVA@γ-PGA-F NPs. Overall, this work indicates that pH responsive α-PGA-F NPs as a carrier adjuvant can effectively improve the ability of cellular immune responses, leading to it being a potent candidate for vaccine applications.     

A mild Cu(I)-catalyzed regioselective diamination of conjugated dienes

This paper describes a novel diamination process that uses CuCl as catalyst and di-tert-butyldiaziridinone as nitrogen source. A wide variety of conjugated dienes and a triene can be effectively diaminated in good yields with generally high regioselectivity under mild reaction conditions.     

Cu(I)-catalyzed intermolecular diamination of activated terminal olefins

This paper describes a novel intermolecular diamination process with CuCl as catalyst and di-tert-butylthiadiaziridine 1,1-dioxide as nitrogen source. A variety of activated terminal olefins can be effectively diaminated in good yields under mild reaction conditions.