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1.
Vianey Vasquez-Ruiz M. Ángeles Ramírez-Cisneros Maria Yolanda Rios 《Magnetic resonance in chemistry : MRC》2022,60(3):275-358
Cedrela genus, a member of the Meliaceae family, presents both chemical characteristics associated with and those that distinguish it from the rest of its members. The presence of triterpenes and limonoids is the characteristic of the Meliaceae family, but the class and type of these chemical constituents are distinctive for each genus. Cedrela includes cycloartane, ursane, oleanane, tirucallane, butyrospermane, and apotirucallane triterpenes, and its limonoids belongs to six class and nine types, known as class Ia-type havanensines, class Ib-type delevoyin, class II-type gedunin, class IIIb-type andirobin, class IIIg-type mexicanolide, class IVa-type evoludone, class Va-type obacunol, class V-type limonin, and class VIII. Each of these structural arrangements includes specific traits, defined by their biosynthetic origin, which can be established by means of structural elucidation techniques, particularly 1H and 13C NMR, which assisted by 2D NMR techniques, allowing to deduce their structures unequivocally. The constant presence of these skeletal arrangements in Cedrela ensures that they are its chemophenetic markers and their recurrence is an important criterion for their identity. This review is a compilation of the occurrence of triterpenes and limonoids in Cedrela genus, detailing their biosynthetic association and collecting and organizing their NMR data, with the purpose of facilitating its location, analysis, and use in the phytochemical study of species from this genus. 相似文献
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3.
Photocatalytic CO2 reduction to C1 fuels is considered to be an important way for alleviating increasingly serious energy crisis and environmental pollution. Due to the environment-friendly, simple preparation, easy formation of highly-stable metal-nitrogen(M-Nx) coordination bonds, and suitable band structure, polymeric carbon nitride-based single-atom catalysts(C3N4-based SACs) are expected to become a potential for CO2 reduction under visible-light irradiation. In this review, we summarize the recent advancement on C3N4-based SACs for photocatalytic CO2 reduction to C1 products, including the reaction mechanism for photocatalytic CO2 reduction to C1 products, the structure and synthesis methods of C3N4-based SACs and their applications toward photocatalytic CO2 reduction reaction(CO2RR) for C1 production. The current challenges and future opportunities of C3N4-based SACs for photoreduction of CO2 are also discussed. 相似文献
4.
Subrata Hazra Somenath Mahato Kanak Kanti Das Dr. Santanu Panda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(44):e202200556
Heteroaryl boronic acids and esters are extremely important and valuable intermediates because of their wide application in the synthesis of marketed drugs and bioactive compounds. Over the last couple of decades, the construction of highly important heteroaryl carbon-boron bonds has created huge attention. The transition-metal-free protocols are more green, less sensitive to air and moisture, and also economically advantageous over the transition-metal-based protocols. The transition-metal-free C−H borylation of heteroarenes and C−X (X=halogen) borylation of heteroaryl halides represents an excellent approach for their synthesis. Also, various cyclization and alkyne activation protocols have been recently established for their synthesis. The goal of this review article is to summarize the existing literature and the current state of the art for transition-metal-free synthesis of heteroaryl boronic acid and esters. 相似文献
5.
《Mendeleev Communications》2022,32(5):629-631
The Michael–Mannich cascade cyclization of cyano olefins, ethyl 4,4,4-trifluoro-3-oxobutanoate, aromatic aldehydes and ammonium acetate provides convenient stereoselective formation of ethyl 5,5-dicyano-4,6-diaryl-2-hydroxy-2-(trifluoromethyl)piperidine-3-carboxylates with fourstereogenic centers and dialkyl 4,6-diaryl-5-cyano-2-hydroxy-2-(trifluoromethyl)piperidine-3,5-dicarboxylates with five stereogenic centers. Ammonium acetate plays dual role, acting as a base and as a nitrogen source. 相似文献
6.
《Mendeleev Communications》2022,32(1):126-128
3-Aryl-5-methylidene-2-thiohydantoins were constructed in one-pot reaction of aryl isothiocyanates and 3-morpholino- alanine in alkaline medium with the subsequent treatment with boiling hydrochloric acid. 相似文献
7.
The present study optimised the ultrasound-assisted extraction (UAE) of bioactive compounds from Amaranthus hypochondriacus var. Nutrisol. Influence of temperature (25.86–54.14 °C) and ultrasonic power densities (UPD) (76.01–273.99 mW/mL) on total betalains (BT), betacyanins (BC), betaxanthins (BX), total polyphenols (TP), antioxidant activity (AA), colour parameters (L*, a*, and b*), amaranthine (A), and isoamaranthine (IA) were evaluated using response surface methodology. Moreover, betalain extraction kinetics and mass transfer coefficients (KLa) were determined for each experimental condition. BT, BC, BX, TP, AA, b*, KLa, and A were significantly affected (p < 0.05) by temperature extraction and UPD, whereas L*, a*, and IA were only affected (p < 0.05) by temperature. All response models were significantly validated with regression coefficients (R2) ranging from 87.46 to 99.29%. BT, A, IA, and KLa in UAE were 1.38, 1.65, 1.50, and 29.93 times higher than determined using conventional extraction, respectively. Optimal UAE conditions were obtained at 41.80 °C and 188.84 mW/mL using the desired function methodology. Under these conditions, the experimental values for BC, BX, BT, TP, AA, L*, a*, b*, KLa, A, and IA were closely related to the predicted values, indicating the suitability of the developed quadratic models. This study proposes a simple and efficient UAE method to obtain betalains and polyphenols with high antioxidant activity, which can be used in several applications within the food industry. 相似文献
8.
Dr. Philipp Niermeier Dr. Jan-Hendrik Lamm Dr. Andreas Mix Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Norbert W. Mitzel 《ChemistryOpen》2019,8(3):304-315
α,ω-Bis(1,8-dichloroanthracen-10-yl)alkanes with (CH2)n-linker units (n=1–4) were synthesized starting from 1,8-dichloroanthracen-10(9H)-one. This was transformed into anthracenes with allyl, bromomethyl and propargyl substituents in position 10; these were converted in various C−C-bond formation reactions (plus hydrogenation), leading to two anthracene units flexibly linked by α,ω-alkandiyl groups. 1,2-Ethandiyl- and 1,3-propandiyl-linked derivatives were functionalized with ethynyl groups in positions 1, 8, 1’ and 8’, and these terminally functionalized by Me3Sn groups using Me2NSnMe3. All linked bisanthracenes were subjected to UV light induced cyclomerization and a series of 9,10 : 9’,10’-photo-cyclomers were obtained. Their thermal cycloreversion and (repeated) switchability was demonstrated. 1,3-Bis{1,8-bis[(trimethylstannyl)ethynyl]anthracen-10-yl}propane served as model compound for photo-switchable acceptor molecules and its open and closed forms were characterized by NMR and DOSY experiments. 相似文献
9.
Konstantinos A. Lazarou Karilys Gonzlez‐Nieves Indranil Chakraborty Raphael G. Raptis 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7402-7406
The P and M enantiomers of the octanuclear [Fe8(μ4‐O)4(μ‐4‐Cl‐pz)12Cl4] complex, having T symmetry, were resolved by temporary substitution of chloride ligands by racemic 4‐sBu‐phenolates and subsequent crystallization, where the (S)‐ and (R)‐phenolates coordinate selectively to the M and P complexes, respectively. The complexes were characterized by circular dichroism analysis and X‐ray structure determination. This work constitutes a rare example of enantiomeric recognition resulting in spontaneous resolution upon crystallization. 相似文献
10.
Shilei Zhao Yihui Yuan Qiuhan Yu Biye Niu Jianhe Liao Zhanhu Guo Ning Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(42):15121-15127
By chemical cross‐linking the amidoxime group onto dual‐surfaces of natural ore materials, namely halloysite nanotubes (HNTs), an efficient adsorbent, AO‐HNTs, is developed. AO‐HNTs show high uranium adsorption capacity of 456.24 mg g?1 in 32 ppm uranium‐spiked simulated seawater. In natural seawater, AO‐HNTs reach the high uranium extraction capacity of 9.01 mg g?1 after 30 days’ field test. The dual‐surface amidoximated hollow nanotubular AO‐HNTs exhibit more coordination active sites for uranium adsorption, which is attributed to the high and fast uranium adsorption capacity. Because of the stable natural ore structure, AO‐HNTs also show long service life. Benefiting from the low cost of HNTs, the cost for uranium extraction from seawater is close to the uranium price in the spot uranium market, suggesting that AO‐HNTs could be used for economical extraction of uranium from the oceans. 相似文献