查看更多>>摘要：Asymmetric aldol reactions of ester-derived titanium enolates of (R)-(N-tosyl)phenylalaninol propionate and bidentate aromatic aldehydes has been investigated. Substrate scope of this aldol reaction was examined with a variety of bidentate aromatic aldehydes to provide syn-aldol products with high diastereoselectivity and isolated yields. Both enantiomers of N-(tosyl)phenylalaninol are readily prepared from commercially available and optically active phenylalaninol. Mild saponification removed the chiral auxiliary and furnished optically active 8-hydroxy carboxylic acids.
查看更多>>摘要：Though the physical blending polymeric preceramic and photosensitive compounds has been proved an easily scaled-up and cost-effective approach to prepare photocurable precursors for most of silicon-based ceramics, there is still scarce of practical photocurable precursor system to SiC ceramic, due to poor com-patibility between polycarbosilane and commercially available photosensitizers. Also, in contrast to intensive research on polymeric precursor, no attention has been paid on development of photosensitive compounds for preceramic polymers. In this work, a series of photosensitive carbosilanes containing Si-C backbone and acrylate group was designed and synthesized, which showed good compatibility with polycarbosilanes. The calculation result on the solubility parameters of the carbosilanes and polycarbosi-lanes well explained their good compatibility. The UV-curing behavior and thermal properties of the pho-tosensitive carbosilanes and their blend systems with polycarbosilanes were also studied. This work provides useful guidelines for selecting and designing photosensitive compounds have good compatibil-ity with preceramic polymers. (c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：Sulfilimines, the aza-analogs of sulfoxides, are valuable building blocks in organic synthesis and serve as important functional groups in medicinal chemistry. Herein we reported an efficient and environmen-tally friendly method of preparing sulfilimines from readily available thioether and sulfonamide as sub-strate. The reaction proceeds via the in-situ produced hypervalent iodine from catalytic simple iodobenzene under electrooxidation conditions. A series of sulfilimines were obtained in moderate to good yields.(c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：A 1,4,2-diazaborole-type heterocycle was obtained via addition of [(alkylamino)methyl]-trifluoroborate to 2H-azirine-2-carboxylate. The molecular structure of the product was confirmed by X-ray crystallog-raphy. The reaction proceeded at ambient temperature without metal catalysts and induced cleavage of the azirine C2-C3 bond without photoirradiation. This product can be regarded as a boron-containing peptidomimetic molecule that has potential applications in medicinal and synthetic chemistry.(c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：Enantioselective construction of the central [3.2.1] oxa-bicyclic core of hedyosumins A-C was achieved via an enantioselective Diels-Alder reaction and a platinum(II)-catalyzed 1,3-dipolar [3+2] cycloaddition as key steps, which leads to the asymmetric total synthesis of hedyosumins A-C. (c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：Two new quinolizidine-based alkaloids, ochrocephalamines E (1) and F (2) were isolated from Oxytropis ochrocephala Bunge (Fabaceae). Their structures were elucidated by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculations. Compound 1 represented the first 14-nor matrine with 6/6/6/5 ring system, while compound 2 shared the aloperine-type scaffold including the carbonyl group at C-10 postition. The inhibitory activities of 2 against the secretion of HBsAg and HBeAg were respectively 22.34 +/- 4.38% and 18.00 +/- 5.01% at the noncytotoxic concentration of 1 x 10-5 mol/L, which were more active than the positive control hyperoside (16.09% and 12.23%). The binding mode between compound 2 and HBV core protein was illustrated by molecular docking. (c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：The development of transition-metal free systems for multi-sites deuteration is important for the preparation of deuterium-labeled drugs and intermediates. We reported that ionic liquid [bmim]PF6 was able to promote highly efficient deuterodeborylation of boronic acids with D2O. The ionic liquid/boronic acid system was successfully applied to the selective H/D exchange at various sp(2)/sp(3) C-H positions. Moreover, unusual nucleophilic behaviors of nitrogen-containing heteroaromatics in ionic liquid were observed. (C) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：We develop an efficient and workable method for the reduction of imines via hydroboration with HBpin. The low cost and non-toxic Fe exhibits high catalytic activity to this hydroboration. A large range of aldimines comprising diverse aryl groups, alkyl groups and heterocycles proceed the hydroboration well to yield secondary amines in good to excellent yields. Kinetic mechanistic studies indicate the importance of Fe in transformation of HBpin into an active species. The preparation of several commercially available pharmaceuticals by means of this strategy highlights its potential application in medicinal chemistry. (c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：An efficient and direct oxidative reaction for the construction of 1,4-dihydroquinoxaline-2,3-diones has been developed. A range of oxidative products are obtained with satisfactory yields (up to 99%). This practical method features transition metal free, surfactant free, chromatography free, mild reaction conditions, good functional group tolerance and easy scale-up synthesis. Furthermore, it provided a convenient approach for the synthesis of one kind of known inhibitor for a-glucosidase. This mechanistic study shows that this transformation is not a radical process. (C) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：A base-promoted cascade radical difluoroalkylation/cyclization of acrylamides with ICF2COOEt to synthesize CF2-containing oxindoles and isoquinoline-1,3-diones in moderate to excellent yields was developed under transition metal-free and catalyst-free conditions. This reaction tolerated a variety of functional groups and provided an alternative and mild method for the preparation of difluoroester-substituted fiveand six-membered nitrogen-containing heterocyclic products.
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