10.1002/adsc.201300049
The research presents an innovative method for the synthesis of aromatic and heteroaromatic diorganozinc reagents using a 2,2,6,6-tetramethylpiperidyl (TMP) magnesium base in conjunction with zinc chloride (ZnCl2), offering a more efficient and mild approach compared to previous methods. The study focuses on accelerating zincations, which are crucial for the functionalization of aromatics and heterocycles. The researchers discovered that moderately elevating the reaction temperature (up to 40°C) significantly reduced the reaction time, with a notable rate acceleration of up to 50 times. This method's generality was demonstrated through the preparation of a variety of polyfunctional diorganozincs by reacting different aromatics and heterocycles with ZnCl2·nLiCl (where n=0, 1, 2) followed by TMPMgCl·LiCl. The resulting zinc reagents were then quenched with electrophiles to yield the expected products in 57–94% yield. The reactions were meticulously monitored, and the temperature was observed to moderately increase upon the addition of TMPMgCl·LiCl to the substrate/ZnCl2 solution. The study also suggests that the observed rate increase could be due to either a Lewis acid activation of the organic substrate followed by magnesiation and rapid transmetalation with ZnCl2 or the generation of a more reactive species at the elevated temperature. The research was funded by the European Research Council and received support from the Fonds der Chemischen Industrie, along with chemical donations from BASF SE, Heraeus Holding GmbH, and Rockwood Lithium GmbH.
10.1002/chem.201200696
The research focuses on the synthesis of tailored metal-organic frameworks (MOFs) using a stepwise strategy with functionalized molecular building blocks (MBBs) and organic linkers of tunable length. The main goal is to enable the design and control of MOF synthesis and, for the first time, functionalize secondary building units (SBUs) and organic linkers within the same MOF. The experiments involved the preparation of tetrahedral MBBs (TMBBs) and a series of quaternary ligands with functional groups and tunable lengths. These were combined to form a diamond-like MOF (DMOF-n). The reactants included nanoscale pentanuclear metal clusters and carefully designed quaternary ligands with various functional groups. Zinc nitrate tetrahydrate ([Zn(NO3)2·4H2O]) and zinc chloride (ZnCl2) were used as metal salts. The structure and properties of the synthesized MOFs were characterized using single crystal X-ray analysis, powder X-ray diffraction (PXRD), and gas adsorption isotherms. The analysis showed that the surface area and hydrogen uptake capacity of the MOFs depend on the optimal combination of functional groups of the SBUs and organic linkers, interpenetration, and free volume within the system.
10.1021/acs.joc.0c01544
The research aims to establish a reagent-controlled protocol for the divergent and regio- and stereo-selective synthesis of C-glycosides, which are carbohydrate units attached to acceptors via carbon atoms instead of oxygen atoms, exhibiting enhanced stability and wide applications in biochemical probes and pharmaceuticals. The study leverages the directing effect of the C3-OH located o-diphenylphosphanylbenzoyl (o-DPPB) group in glycals to achieve α- and β-C-glycosides through a syn-SN2’ or anti-SN2’ mechanism, respectively. The researchers successfully demonstrated that the introduction of ZnCl2 additive can silence the directing effect of the o-DPPB group, enabling the selective synthesis of α-C-glycosides. The chemicals used in the process include various glycals, Grignard reagents, CuBr?SMe2 as a catalyst, and ZnCl2 as an additive to control the stereoselectivity of the reaction. The conclusions highlight the scalability and flexibility of the developed protocol, which may have broad applications in the synthesis of C-glycosides.
10.1021/jo034719b
The research explores the chemoselectivity of electron-poor indoles in [4 + 2] cycloadditions, focusing on the competition between Diels-Alder (DA) and hetero-Diels-Alder (HDA) reactions. The study aims to demonstrate the influence of electronic and structural parameters on the reactivity of indoles, leading to either DA or HDA products. The researchers used various indole derivatives, such as indole-3-carboxaldehyde, indole-3-glyoxalate, and N-substituted indole-3-glyoxamides, along with dienes like 2,3-dimethylbutadiene and Danishefsky diene. The reactions were activated thermally, under high pressure, or with the aid of Lewis acids like zinc chloride and europium tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) (EuFOD). The conclusions highlight the ability to modulate the reactivity of the indole dienophile to favor either the classical DA process or the HDA reaction, with the products strongly depending on the type of electron-withdrawing substituent on the indole, the diene used, and the activation method. The study also reveals a remarkable reversal of chemoselectivity based on the number and nature of substituents on the acyclic nitrogen atom of the indole-3-glyoxamides.
10.1007/BF00909177
The study investigates the alkenylation of m-cresol by allyl alcohol using various acid catalysts, including phosphoric acid, zinc chloride deposited on aluminum oxide, and cationite KU-1. The researchers found that under certain conditions, the yield of alkenylation products could reach 47% of the theoretical value. The reaction products include isomeric allyl-m-cresols and 2,6-dimethylcoumaran. The study also explores the reaction mechanism, suggesting that the alkenylation proceeds via both C-alkenylation and O-alkenylation pathways, with the O-alkenylation product rearranging to form the ortho isomer and subsequently cyclizing to 2,6-dimethylcoumaran.
10.1021/ja056076i
The study presents a novel method for the intermolecular R-arylation and vinylation of amides through palladium-catalyzed coupling of aryl and vinyl bromides with zinc enolates of amides. The researchers developed reactions using three different types of zinc enolates, achieving high yields with a variety of bromoarenes, including those with functional groups such as cyano, nitro, ester, keto, fluoro, hydroxyl, or amino. The use of zinc enolates, as opposed to alkali metal enolates, significantly expands the scope of amide arylation by allowing reactions at room temperature or 70 °C and by tolerating a broader range of functional groups. The study also introduces the use of morpholine amides, which are precursors to ketones and aldehydes, in the arylation process. The reactions were facilitated by catalysts bearing hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) or the highly reactive, dimeric Pd(I) complex {[P(t-Bu)3]PdBr}2, offering a mild and efficient approach to synthesize R-aryl carbonyl compounds, which are prevalent in pharmaceuticals and biologically active compounds.
10.1021/ic2012205
The research focuses on the development of bifunctional stilbene derivatives, L1-a and L1-b, designed to target and modulate metal-amyloid-β (Aβ) species, which are implicated in the pathogenesis of Alzheimer's disease (AD). The study involves a rational structure-based design approach that incorporates a metal binding site into the structure of an Aβ interacting molecule. The experiments conducted include UV-vis spectroscopy, X-ray crystallography, high-resolution 2D NMR, and docking studies to explore the reactivity of these compounds towards metal-Aβ species. The analyses used assess the compounds' ability to modulate metal-induced Aβ aggregation, neurotoxicity, and ROS (reactive oxygen species) production in vitro and in living cells. The reactants include Aβ peptides, metal chloride salts (CuCl2 or ZnCl2), and the synthesized bifunctional compounds L1-a and L1-b. The research provides insights into the structure-interaction-reactivity relationship, which is essential for designing small molecules to target metal-Aβ species and modulate their associated neurotoxicity and aggregation pathways.
10.1016/S0040-4039(00)87909-5
The study in the literature presents a new one-pot synthesis method for 3-amino-β-lactams, which are valuable intermediates for producing various β-lactam antibiotics, including penicillins and cephalosporins. The key chemicals involved are zinc enolates derived from N-protected amino acid esters and imines. Specifically, the zinc enolates are prepared in situ from the corresponding lithium enolates via transmetallation with zinc dichloride. These enolates then react with imines to form the desired 3-amino-β-lactams. The study highlights the high yields and trans-stereoselectivity of this synthetic route, which contrasts with reactions involving lithium enolates. The authors also note that the enolates derived from 2,2,5,5-tetramethyl-1-aza-2,5-disilacyclopentane-1-acetic acid ethyl ester (STABASE) are more stable and yield better results than those from N,N-bis(trimethylsilyl)glycine ethyl ester. The study provides detailed procedures and characterizations of the synthesized compounds, and it suggests that the trans-stereoselectivity arises from a rigid cyclic chair-like transition state of the enolate with an E-imine.
Xn,
C,
N
C:Corrosive;
