Compile the | Li Yan
Science, 15 APR 2022, VOL 376, ISSUE 6590
Science, April 15, 2022, Vol. 376, No. 6590
Chemistry Chemistry
Allylic C–H amination cross-coupling furnishes tertiary amines by electrophilic metal catalysis
Allyl C-H aminated crosslinking is catalyzed to produce tertiary amines by electrophilic metals
▲ 作者：SIRAJ Z. ALI, BRENNA G. BUDAITIS, DEVON F. A. FONTAINE et al.
▲ Link:
https://www.science.org/doi/10.1126/science.abn8382
▲ Abstract:
The cross-coupling of terminal olefins to secondary amine molecules to form complex tertiary amines (a common motif in drug synthesis) remains a challenge in chemical synthesis. Here, we report an allium(II)-catalyzed allyl carbon-hydrogenamine cross-coupling reaction.
It is characterized by 48 cyclic and non-cyclic secondary amines (10 associated nuclei) and 34 terminal olefins (with electrophilic function), synthesizing 81 tert-allylamines, including 12 drug compounds and 10 complex drug derivatives, and has good regional selectivity and stereoselectivity.
▲ Abstract：
Intermolecular cross-coupling of terminal olefins with secondary amines to form complex tertiary amines—a common motif in pharmaceuticals—remains a major challenge in chemical synthesis. Here, we report a palladium(II)-catalyzed allylic carbon-hydrogen amination cross-coupling using this strategy, featuring 48 cyclic and acyclic secondary amines (10 pharmaceutically relevant cores) and 34 terminal olefins (bearing electrophilic functionality) to furnish 81 tertiary allylic amines, including 12 drug compounds and 10 complex drug derivatives, with excellent regio- and stereoselectivity (>20:1 linear:branched, >20:1 E: Z).
Ambient-pressure synthesis of ethylene glycol catalyzed by C60-buffered Cu/SiO2
C60 buffered copper-based catalysts enable atmospheric synthesis of glycol
▲ 作者:JIANWEI ZHENG, XLELE HUANG, CUN-HAO CUI et al.
▲ Link:
https://www.science.org/doi/10.1126/science.abm9257
▲ Abstract:
Chemicals such as glycol (EG) can be industrially synthesized from ethylene or syngas, but syngas experience bottleneck reactions and require high-pressure hydrogen. We found that fullerene, represented by C60, can be used as an electron buffer for copper-based catalysts (Cu/SiO2).
Under atmospheric pressure conditions of 180°~190°C, the yield of ethylene glycol of dimethyl oxalate can reach 98±1% by C60-Cu/SiO2 catalysis. In the kilogram reaction, the catalyst is not inactivated after 1000 hours. This gentle way of producing glycol can be combined with already industrialized environmental reactions, from syngas to intermediates of dimethyl oxalate.
▲ Abstract：
Bulk chemicals such as ethylene glycol (EG) can be industrially synthesized from either ethylene or syngas, but the latter undergoes a bottleneck reaction and requires high hydrogen pressures. We show that fullerene (exemplified by C60) can act as an electron buffer for a copper-silica catalyst (Cu/SiO2). Hydrogenation of dimethyl oxalate over a C60-Cu/SiO2 catalyst at ambient pressure and temperatures of 180° to 190°C had an EG yield of up to 98 ± 1%. In a kilogram-scale reaction, no deactivation of the catalyst was seen after 1000 hours. This mild route for the final step toward EG can be combined with the already-industrialized ambient reaction from syngas to the intermediate of dimethyl oxalate.
Amplification of light within aerosol particles accelerates in-particle photochemistry
The amplification of light within the aerosol particles accelerates the photochemical processes within the particles
▲ 作者:PABLO CORRAL ARROYO, GRÉGORY DAVID, PETER A. ALPERT et al.
▲ Link:
https://www.science.org/doi/10.1126/science.abm7915
▲ Abstract:
The light field of the light seal (OC) structure and the amplification of the light intensity inside the atmospheric aerosol particles have an important impact on the photo-driven chemical process of the aerosol. Although it has been theorized, the spatial structure of OC induction has not been observed experimentally so far.
Here, X-ray spectroscopic imaging, combined with modeling, provides direct evidence for patterns of OC induction within photoactive particles. Single iron(III)-citric acid particles are detected using the iron oxidation state as a photochemical marker.
Based on these results, we predict that the overall acceleration of photochemical reactions in most kinds of aerosol particles will be 2 to 3 times. The rotation of free aerosol particles and the transport of molecules within particles usually accelerate photochemical processes. Given the pervasiveness of the OC effect, atmospheric models should consider its effect on the photochemical processes of aerosol particles.
▲ Abstract：
Optical confinement (OC) structures the optical field and amplifies light intensity inside atmospheric aerosol particles, with major consequences for sunlight-driven aerosol chemistry. Although theorized, the OC-induced spatial structuring has so far defied experimental observation. Here, x-ray spectromicroscopic imaging complemented by modeling provides direct evidence for OC-induced patterning inside photoactive particles. Single iron(III)–citrate particles were probed using the iron oxidation state as a photochemical marker. Based on these results, we predict an overall acceleration of photochemical reactions by a factor of two to three for most classes of atmospheric aerosol particles. Rotation of free aerosol particles and intraparticle molecular transport generally accelerate the photochemistry. Given the prevalence of OC effects, their influence on aerosol particle photochemistry should be considered by atmospheric models.
Materials Science
Volumetric additive manufacturing of silica glass with microscale computed axial lithography
Microscale calculations for volumetric additive manufacturing of silicon glass on axial lithography
▲ 作者：JOSEPH T. TOOMBS, MANUEL LUITZ, CAITLYN C. COOK et al.
▲ Link:
https://www.science.org/doi/10.1126/science.abm6459
▲ Abstract:
From micro-optics for consumer products to microfluidic systems for chemical synthesis and bioanalysis, glass is becoming increasingly popular as a material for manufacturing complex microgeomic shapes. Traditional processing methods have been challenged as glass size, geometry, surface roughness and mechanical strength requirements have evolved.
We introduce microscale axial computational lithography (micro-CAL) for molten silica elements, which performs tomography of subsequently sintered photopolymer-silica nanocomposites. We fabricated three-dimensional microfluidics with an inner diameter of 150 microns, freeform microoptics with a surface roughness of 6 nanometers, and complex high-strength trusses and lattice structures with a minimum feature size of 50 microns.
As a high-speed digital light manufacturing process, micro-CAL can process nanocomposites with high solids content and high geometric freedom, realizing new device structures and applications.
▲ Abstract：
Glass is increasingly desired as a material for manufacturing complex microscopic geometries, from the micro-optics in compact consumer products to microfluidic systems for chemical synthesis and biological analyses. As the size, geometric, surface roughness, and mechanical strength requirements of glass evolve, conventional processing methods are challenged. We introduce microscale computed axial lithography (micro-CAL) of fused silica components, by tomographically illuminating a photopolymer-silica nanocomposite that is then sintered. We fabricated three-dimensional microfluidics with internal diameters of 150 micrometers, free-form micro-optical elements with a surface roughness of 6 nanometers, and complex high-strength trusses and lattice structures with minimum feature sizes of 50 micrometers. As a high-speed, layer-free digital light manufacturing process, micro-CAL can process nanocomposites with high solids content and high geometric freedom, enabling new device structures and applications.
Geoscience for Earth Sciences
Citizen seismology helps decipher the 2021 Haiti earthquake
Citizen seismology helps decipher the 2021 Haiti earthquake
▲ 作者:E. CALAIS, S. SYMITHET. MONFRET, B. DELOUIS et al.
▲ Link:
https://www.science.org/doi/10.1126/science.abn1045
▲ Abstract:
The magnitude 7.2 earthquake in Haitian's Neps province on August 14, 2021, occurred in the same fault zone as the devastating 2010 magnitude 7.0 earthquake, but the earthquake still struck the country due to unsafe rescue constraints and the inability of conventional seismometers in the national network to work.
However, the civil seismometer network installed in 2019 provides near-field data that is critical to quickly understanding the main seismological mechanism and monitoring the rest of the seismic sequence. Their real-time data defined two aftershock groups and coincided with two coseismic sliding regions derived from inversion of traditional seismic and geodetic data.
By applying machine learning to data from the civil seismometer closest to the main quake, we can predict aftershocks as accurately as we would using a network-derived catalog. This shows the role of citizen science in helping us understand large earthquakes.
▲ Abstract：
On 14 August 2021, the moment magnitude (Mw) 7.2 Nippes earthquake in Haiti occurred within the same fault zone as its devastating 2010 Mw 7.0 predecessor, but struck the country when field access was limited by insecurity and conventional seismometers from the national network were inoperative. A network of citizen seismometers installed in 2019 provided near-field data critical to rapidly understand the mechanism of the mainshock and monitor its aftershock sequence. Their real-time data defined two aftershock clusters that coincide with two areas of coseismic slip derived from inversions of conventional seismological and geodetic data. Machine learning applied to data from the citizen seismometer closest to the mainshock allows us to forecast aftershocks as accurately as with the network-derived catalog. This shows the utility of citizen science contributing to our understanding of a major earthquake.
Neuroscience
Compartmentalized dendritic plasticity during associative learning
Distinguish dendritic plasticity in associative learning
▲ 作者:SIMON D'AQUIN, ANDRAS SZONYI, MATHIAS MAHN et al.
▲ Link:
https://www.science.org/doi/10.1126/science.abf7052
▲ Abstract:
Behavioral changes that rely on experience are regulated by long-term functional modifications in brain circuits. Activity-dependent plasticity of synaptic input is a major cellular-based process.
While we have a detailed understanding of synaptic and dendritic plasticity in vitro, little is known about the active dendritic function and plasticity of active organisms. Using deep brain two-photon calcium imaging, we investigated how the classical fear conditioning affects how sensory responses are generated in the main neurons of the amygdala.
Fear conditioning induces differences in dendrites and somatic plasticity regulated by chamber-specific inhibition. Our findings suggest that learning-induced plasticity can be decoupled between in vivo and dendrites, reflecting different synapse and microcircuit-level mechanisms, increasing the computational power of the amygdala circuit.
▲ Abstract：
Experience-dependent changes in behavior are mediated by long-term functional modifications in brain circuits. Activity-dependent plasticity of synaptic input is a major underlying cellular process. Although we have a detailed understanding of synaptic and dendritic plasticity in vitro, little is known about the functional and plastic properties of active dendrites in behaving animals. Using deep brain two-photon Ca2+ imaging, we investigated how sensory responses in amygdala principal neurons develop upon classical fear conditioning, a form of associative learning. Fear conditioning induced differential plasticity in dendrites and somas regulated by compartment-specific inhibition. Our results indicate that learning-induced plasticity can be uncoupled between soma and dendrites, reflecting distinct synaptic and microcircuit-level mechanisms that increase the computational capacity of amygdala circuits.