查看更多>>摘要：An efficient synthesis for a new conformationally locked chiral cis-1,2-diaminocyclohexane scaffold has been developed. The conformational lock allows for convenient symmetrical derivatization of the amino groups through the reductive amination strategy. A series of optically pure chiral ligands based on the cis-DACH scaffold has been generated to demonstrate a proof-of-concept for these ligands as chiral catalysts in the asymmetric Henry reaction. Excellent yields with moderate enantioselectivity were demonstrated at room temperature, with an increase in enantioselectivity at lower temperatures, showing the potential of this new type of cis-DACH ligand.(c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：Transition metal catalyzed chemical transformations have appeared as one of the key innovations in syn-thetic chemistry, which also been widely applied in drug discovery, agricultural chemistry and material science. Comparing to widely investigated ionic mechanism, transition metal catalyzed radical reactions are less explored, but they be used as an alternative approach to construct challenging carbon-carbon and carbon-heteroatom bonds. This digest paper highlights recent advances in merging halogen-atom transfer (XAT) with transition metal catalysis and mainly focuses on nickel, copper, cobalt and iron cat-alyzed radical reactions.(c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：Organocatalysis by the combination of weak acids, namely, 2,20-biphenol and B(OH)3, for 2-aza-Cope rearrangement is described. Aldehydes and 1,1-diphenyl homoallylamine were converted into the corre-sponding homoallylamines in moderate-to-high yield in the presence of 10 mol% 2,20-biphenol and 30 mol% B(OH)3. In contrast to the conventional 2-aza-Cope rearrangement catalyzed by strong activa-tors, a user-and environment-friendly organocatalytic system was established using a combination of inexpensive, easy-to-handle, non-hazardous, and bench-stable reagents.(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：An efficient metal-free method for the synthesis of symmetrical 1,3-diynes through iodine-mediated decarboxylative homocoupling of aryl propiolic acids was developed. This iodine-mediated decarboxyla-tive homocoupling reaction by Csp-Csp bond formation in DMSO underwent smoothly to afford the cor-responding 1,4-disubstituted 1,3-dialkynes in good to excellent yields. This operationally simple and environmentally benign protocol avoids the use of sophisticated ligands, additional oxidants and expen-sive transition metal/reagents.(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：This report describes the mild electrochemical metal-, oxidant-, additive-free site-selective direct C-H amidation of benzyl C(sp3)-H bonds in an undivided cell using a-amino acids as a source of an amide bond moiety. Practically significant amides are obtained under electrochemical mild one-pot conditions (without strong external oxidants, at room temperature), with total yields up to 73%. This electrochem-ical approach features a functional selectivity and a broad scope of substrates with benzyl bond and dif-ferent amino acids.(c) 2022 Elsevier Ltd. All rights reserved.
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：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：Reactions of beta-formyl-beta-nitroenamine with anilines afforded N,N'-diaryl-alpha-nitro-beta-dialdimines; however, only small amounts of dialdimines were obtained when anilines possessing an electron-withdrawing group were employed. This disadvantage was overcome by adding anilinium salts to control the equilibrium, which resulted in the formation of dialdimines in considerably improved yields. This method facilitated to introduce less nucleophilic 5-bromopyrid-2-yl groups that are expected to be a precursor for various frameworks. The prepared dialdimines served as a ligand which formed the nickel(II) complex with a distorted tetrahedral structure. (C) 2022 Elsevier Ltd. All rights reserved.
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