α-Carbonyl Rh-Carbenoid Initiated Cascade Assembly of Diazobarbiturates with Alkylidene Pyrazolones for Synthesis of Spirofuropyrimidines.

Catalyzed by Rh2(esp)2 (10 mol%) and (±)-BINAP (20 mol%) in DCE at 80 °C, the cascade assembly between diazobarbiturates and alkylidene pyrazolones proceeded readily and produced spiro-furopyrimidines in 38-96% chemical yields. The chemical structure of the prepared spirofuro-pyrimidines was firmly confirmed by X-ray diffraction analysis.

Diastereoselective Cascade Cyclization of Diazoimides with Alkylidene Pyrazolones for Preparation of Pyrazole-Fused Oxa-Bridged Oxazocines.

Under the catalysis of Rh2(OAc)4 (10 mol%) and binapbisphosphine ligand (±)-L3 (20 mol%) in DCE at 80 °C, the cascade cyclization of diazoimides with alkylidenepyrazolones underwent stereoselectively (dr > 20:1), affording pyrazole-fused oxa-bridged oxazocines in reasonable chemical yields. The chemical structure and relative configuration of title products were firmly identified by X-ray diffraction analysis.

Pd-catalyzed decarboxylative 1,4-addition reactions of benzofuran-based azadienes with allyl phenyl carbonates.

Under the catalysis of Pd(OAc)2/dppf/Na2CO3, the decarboxylative 1,4-addition reaction of benzofuran-based azadienes with allyl phenyl carbonates took place easily and delivered the desired products in reasonable chemical yields. The chemical structure of the target compounds was clearly identified by single crystal X-ray structural analysis.

Pd-Catalyzed three-component decarboxylative coupling reactions between alkylidene pyrazolones, allyl carbonates and active methylene compounds.

Under the catalysis of Pd2(dba)3·CHCl3/(±)-L5 in THF at room temperature, the three-component decarboxylative coupling reactions among alkylidene pyrazolones, allyl carbonates and active methylene compounds proceeded readily and furnished the desired products in acceptable chemical yields. The chemical architecture of the obtained products was unambiguously confirmed by single crystal X-ray analysis.

Switching magnon chirality in artificial ferrimagnet.

Chirality, an intrinsic degree of freedom, has been barely exploited as the information carriers in data transmission, processing, computing, etc. Recently the magnons in antiferromagnets were proposed to carry both right-handed and left-handed chiralities, shedding a light on chirality-based spintronics in which chirality-based computing architectures and chiral magnonic devices may become feasible. However, the practical platform for chirality-based spintronics remains absent yet. Here we report an artificial ferrimagnetic Py/Gd/Py/Gd/Py/Pt multilayer by which the switching, reading, and modulation of magnon chirality are demonstrated. In particular, the coexisting resonance modes of ferromagnetic and antiferromagnetic characteristics permit the high adjustability and easy control of magnon chirality. As a main result, we unambiguously demonstrated that Py precessions with opposite chiralities pump spin currents of opposite spin polarizations into the Pt layer. Our result manifests the chirality as an independent degree of freedom and illustrates a practical magnonic platform for exploiting chirality, paving the way for chirality-based spintronics.

Palladium-Catalyzed Formal (5 + 6) Cycloaddition of Vinylethylene Carbonates with Isatoic Anhydrides for the Synthesis of Medium-Sized N,O-Containing Heterocycles.

Under the reaction conditions of Pd(PPh3)4 (2.5 mol %) and PPh3 (10 mol %) in EtOAc at 60 °C, the formal (5 + 6) cycloaddition of vinylethylene carbonates with isatoic anhydrides proceeded smoothly and furnished medium-sized N,O-containing heterocycles in reasonable chemical yields. The chemical structures of the title products were clearly identified by X-ray diffraction analysis.

Asymmetric Synthesis of Spiropyrazolones via Chiral Pd(0)/Ligand Complex-Catalyzed Formal [4+2] Cycloaddition of Vinyl Benzoxazinanones with Alkylidene Pyrazolones.

In the presence of the chiral Pd(0)/ligand complex, vinyl benzoxazinanones underwent the [4+2] cycloaddition with alkylidene pyrazolones smoothly and delivered spiropyrazolones in reasonable yields, diastereoselectivities, and eneantioselectivities (up to >99% yield, >99:1 dr and 99% ee). The absolute configuration of the obtained spiropyrazolones was unambiguously characterized with the use of X-ray single-crystal structure analysis. Moreover, the reaction mechanism was assumed to interpret the formation of the target compounds.

Photocatalyst-Free Singlet Oxygen-Induced Oxygenation: A Strategy for the Preparation of 5-Cyano-2-pyridones Driven by Blue-Light Irradiation.

A mild, catalyst- and metal-free photochemical protocol for the oxygenation of 3-cyano-1,4-dihydropyridines to 5-cyano-2-pyridones was developed. Utilizing molecular oxygen from the air as the oxidant and a cheap blue LED lamp as the light source, a variety of 3-cyano-1,4-dihydropyridines were converted into the corresponding 5-cyano-2-pyridones in moderate to excellent yields. Exploration of the substrate scope revealed that 3-cyano and 4-aryl groups play an important role in the formation of 2-pyridone.

Formal [5+2] cycloaddition of vinylethylene carbonates to oxazol-5-(4H)-ones for the synthesis of 3,4-dihydrooxepin-2(7H)-ones.

Under the catalysis of Pd2(dba)3 (2.5 mol%), PPh3 (10.0 mol%) and TMSCl (1.0 eq.), the formal [5+2] cycloaddition of vinylethylene carbonates to oxazol-5-(4H)-ones proceeded readily in THF at 60 °C to r.t., thus furnishing 3,4-dihydrooxepin-2(7H)-ones in 67-99% chemical yields. The chemical structure of one compound was confirmed by X-ray diffraction analysis, and the others were suggested by inference.

Diastereoselective and Enantioselective Synthesis of Barbiturate-Fused Spirotetrahydroquinolines via Chiral Palladium(0)/Ligand Complex Catalyzed [4 + 2] Cycloaddition of Vinyl Benzoxazinanones with Barbiturate-Based Olefins.

Under the catalysis of chiral palladium(0)/ligand complex, the [4 + 2] cycloaddition between vinyl benzoxazinanones and barbiturate-based olefins proceeded readily and provided barbiturate-fused spirotetrahydroquinolines in up to 96% chemical yield with up to >99:1 dr and 97% ee. The absolute configuration of barbiturate-fused spirotetrahydroquinolines was clearly identified by X-ray single crystal structure analysis. The reaction mechanism was proposed to shed light on the enantioselective formation of barbiturate-fused spirotetrahydroquinolines.

[3 + 2] Cycloaddition of Oxazol-5-(4H)-ones with Nitrones for Diastereoselective Synthesis of Isoxazolidin-5-ones.

In the presence of TMSCl, the [3 + 2] cycloaddition of oxazol-5-(4H)-ones with nitrones proceeded smoothly and furnished the desired isoxazolidin-5-ones with high diastereoselectivities in reasonable chemical yields. The chemical structure of the title compounds was firmly confirmed by X-ray single-crystal structure analysis.

Diastereoselective 1,3-Dipolar Cycloadditions of N,N'-Cyclic Azomethine Imines with Iminooxindoles for Access to Oxindole Spiro-N,N-bicyclic Heterocycles.

In the presence of CuI, 1,3-dipolar cycloadditions of N,N'-cyclic azomethine imines with iminooxindoles proceeded readily and furnished novel oxindole spiro-N,N-bicyclic heterocycles in moderate to excellent chemical yields with excellent diastereoselectivities.

Photogenerated Intrinsic Free Carriers in Small-molecule Organic Semiconductors Visualized by Ultrafast Spectroscopy.

Confirmation of direct photogeneration of intrinsic delocalized free carriers in small-molecule organic semiconductors has been a long-sought but unsolved issue, which is of fundamental significance to its application in photo-electric devices. Although the excitonic description of photoexcitation in these materials has been widely accepted, this concept is challenged by recently reported phenomena. Here we report observation of direct delocalized free carrier generation upon interband photoexcitation in highly crystalline zinc phthalocyanine films prepared by the weak epitaxy growth method using ultrafast spectroscopy. Transient absorption spectra spanning the visible to mid-infrared region revealed the existence of short-lived free electrons and holes with a diffusion length estimated to cross at least 11 molecules along the π-π stacking direction that subsequently localize to form charge transfer excitons. The interband transition was evidenced by ultraviolet-visible absorption, photoluminescence and electroluminescence spectroscopy. Our results suggest that delocalized free carriers photogeneration can also be achieved in organic semiconductors when the molecules are packed properly.

Diastereoselective Synthesis of Dispirobarbiturates through Et3N-Catalyzed [3 + 2] Cycloaddition of Barbiturate-Based Olefins with 3-Isothiocyanato Oxindoles.

Under catalysis of 10 mol % of Et3N, the [3 + 2] cycloaddition of barbiturate-based olefins with 3-isothiocyanato oxindoles underwent smoothly and afforded the desired dispirobarbiturates in up to 99% yield with up to 99:1 dr. The relative configuration of the dispirobarbiturates was unambiguously determined by X-ray single-crystal structure analysis. The reaction mechanism was proposed to shed light on the diastereoselective formation of the dispirobarbiturates.

Enantioselective synthesis of diversely substituted quaternary 1,4-benzodiazepin-2-ones and 1,4-benzodiazepine-2,5-diones.

Benzodiazepines are privileged scaffolds in medicinal chemistry, but enantiopure examples containing quaternary stereogenic centers are extremely rare. We demonstrate that installation of the di(p-anisyl)methyl (DAM) group at N1 of 1,4-benzodiazepin-2-ones and 1,4-benzodiazepine-2,5-diones derived from enantiopure proteinogenic amino acids allows retentive replacement of the C3-proton via a deprotonation/trapping protocol. A wide variety of carbon and nitrogen electrophiles function well in this reaction, providing the corresponding quaternary benzodiazepines with excellent enantioselectivity. Deprotonation/trapping experiments on a pair of diastereomeric 1,4-benzodiazepine-2,5-diones provide evidence for a key role of conformational chirality in these enantioselective reactions. Acidic removal of the DAM group is fast and high-yielding and can be performed selectively in the presence of a N-Boc indole. Thus the synthesis of quaternary benzodiazepines with diverse N1 functionality can now be accomplished.

Enantioselective synthesis of "quaternary" 1,4-benzodiazepin-2-one scaffolds via memory of chirality.

Glycine-derived 1,4-benzodiazepine-2-ones such as diazepam are chiral by virtue of the boat-shaped conformation of the diazepine ring and exist as a racemic mixture of conformational enantiomers. However, the presence of a chiral center at C-3 of the benzodiazepine perturbs this equilibrium and preferentially stabilizes one ring conformer. We report that N-i-Pr 1,4-benzodiazepine-2-ones derived from (S)-Ala and (S)-Phe can be deprotonated and alkylated in 86-99% ee, despite the fact that the original chiral center is destroyed in the deprotonation step. We attribute this highly enantioselective alkylation to the chiral memory of the benzodiazepine ring. This protocol provides easy access to the previously unexplored "quaternary" 1,4-benzodiazepine-2-ones.