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Diversity in Gold‐Catalyzed Formal Cycloadditions of Ynamides with Azidoalkenes or 2H‐Azirines: [3+2] versus [4+3] Cycloadditions 下载免费PDF全文
Samir Kundlik Pawar Rajkumar Lalji Sahani Prof. Dr. Rai‐Shung Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10843-10850
Gold‐catalyzed cycloadditions of ynamides with azidoalkenes or 2H‐azirines give [3+2] or [4+3] formal cycloadducts of three classes. Cycloadditions of ynamides with 2H‐azirine species afford pyrrole products with two regioselectivities when the Cβ‐substituted 2H‐azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron‐rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3] cycloadditions to deliver 1H‐benzo[d]azepine products instead. 相似文献
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Keita Sakamoto Akihiro Hakamata Prof. Dr. Masashi Tsuda Prof. Dr. Haruhiko Fuwa 《Angewandte Chemie (International ed. in English)》2018,57(14):3801-3805
Total syntheses of the proposed and correct structures of iriomoteolide‐2a, a cytotoxic marine macrolide natural product with an unusual 23‐membered macrolactone skeleton, have been accomplished for the first time. The synthesis of the correct structure involves an asymmetric epoxidation/diepoxide cyclization cascade for the construction of the bis(tetrahydrofuran) moiety, a Suzuki–Miyaura coupling for the fragment assembly, and a ring‐closing metathesis for the closure of the macrocyclic backbone. In addition, the original stereochemical assignment of iriomoteolide‐2a was revised. 相似文献
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Ying Wang Prof. Dr. Shilie Pan Yunjing Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(38):12046-12051
A new series of anhydrous mixed alkali‐metal borophosphates—Li2Cs2B2P4O15 ( 1 ), LiK2BP2O8 ( 2 ), Li3K2BP4O14 ( 3 ), and Li3Rb2BP4O14 ( 4 )—have been successfully synthesized by using the conventional solid‐state reaction method. Compound 1 contains a novel fundamental building unit (FBU), [B4P8O30], with B/P=1:2. Compound 2 contains an FBU of [B2P4O16] with B/P=1:2. Compounds 3 and 4 are isotypic, and they have a [B(P2O7)2] unit as their FBU. In all four compounds, their FBUs are connected through corner sharing to generate layered anionic partial structures, and then further linked with metallic polyhedra to form three‐dimensional (3D) frameworks. Most interestingly, three of the four compounds contain direct P‐O‐P connections in their structures, which is extremely rare among borophosphates. Thermal analyses, IR spectroscopy, and UV/Vis/near‐IR diffuse reflectance spectroscopy have also been performed on the four title compounds. 相似文献
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Gold(I)‐Catalyzed Generation of the Two Components of a Formal [4+2] Cycloaddition Reaction for the Synthesis of Tetracyclic Pyrano[2,3,4‐de]chromenes 下载免费PDF全文
Dr. Tamara Arto Prof. Dr. Francisco J. Fañanás Prof. Félix Rodríguez 《Angewandte Chemie (International ed. in English)》2016,55(25):7218-7221
Ortho‐Alkynylbenzaldehydes have been widely used to generate isochromenylium derivatives through gold‐catalyzed cycloisomerization. These isochromenylium derivatives have been exploited as formal diene derivatives for reactions with different dienophiles. Herein, we describe the behavior of ortho‐alkynylsalicylaldehydes, a particular case of ortho‐alkynylbenzaldehydes. The gold‐catalyzed cycloisomerization of ortho‐alkynylsalicylaldehydes delivers an unusual heterodiene derivative that reacts with electron‐rich alkenes through a formal [4+2] cycloaddition. In this reaction, both the diene and dienophile are generated in situ through gold‐catalyzed cycloisomerization of appropriate alkynamines or alkynols. This reaction was used to synthesize complex tetracyclic pyrano[2,3,4‐de]chromenes from two very simple starting materials (an ortho‐alkynylsalicylaldehyde and an alkynamine or alkynol) with complete atom economy and with selective formation of bonds, cycles, and stereocenters. 相似文献
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Functionalization of P4 Using a Lewis Acid Stabilized Bicyclo[1.1.0]tetraphosphabutane Anion 下载免费PDF全文
Jaap E. Borger Dr. Andreas W. Ehlers Dr. Martin Lutz Dr. J. Chris Slootweg Prof. Dr. Koop Lammertsma 《Angewandte Chemie (International ed. in English)》2014,53(47):12836-12839
Reacting white phosphorus (P4) with sterically encumbered aryl lithium reagents (aryl=2,6‐dimesitylphenyl or 2,4,6‐tBu3C6H2) and B(C6F5)3 gives the unique, isolable Lewis acid stabilized bicyclo[1.1.0]tetraphosphabutane anion. Subsequent alkylation of the nucleophilic site of the RP4 anion gives access to non‐symmetrical disubstituted bicyclic tetraphosphorus compounds. This novel method enables P? C bond formation in a controlled fashion using white phosphorus as starting material. 相似文献
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Chi‐Shin Wang Yu‐Chen Wei Kai‐Hsin Chang Pi‐Tai Chou Yao‐Ting Wu 《Angewandte Chemie (International ed. in English)》2019,58(30):10158-10162
Indeno[1,2‐b]fluorene‐based [2,2]cyclophanes with 4n/4n and 4n/[4n+2] π‐electron systems were prepared, and their structures were identified by X‐ray crystallography. With short π–π distances around 3.0 Å, [2.2](5,11)indeno[1,2‐b]fluorenophane and its precursor [2.2](5,11)indeno[1,2‐b]fluorene‐6,12‐dionophane exhibit remarkable transannular interactions, leading to their unusual electrochemical and photophysical properties. With the aid of femtosecond transient absorption spectroscopy, the transition from the monomeric excited state to the redshifted H‐type dimeric state was first observed, correlating to the calculated excitonic energy splitting and the steady‐state absorption spectra induced by charge‐transfer‐mediated superexchange interaction. 相似文献
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Copper Nitrate Mediated Regioselective [2+2+1] Cyclization of Alkynes with Alkenes: A Cascade Approach to Δ2‐Isoxazolines 下载免费PDF全文
Mingchun Gao Yingying Li Yuansheng Gan Prof. Dr. Bin Xu 《Angewandte Chemie (International ed. in English)》2015,54(30):8795-8799
An efficient method for the regioselective synthesis of pharmacologically relevant polysubstituted Δ2‐isoxazolines is based on the copper‐mediated direct transformation of simple terminal alkynes and alkenes. The overall process involves the formation of four chemical bonds with inexpensive and readily available copper nitrate trihydrate as a novel precursor of nitrile oxides. The reaction can be easily handled and proceeds under mild conditions. 相似文献
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Juliane Schoening Alexander Gehlhaar Dr. Christoph Wölper Prof. Dr. Stephan Schulz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(41):e202201031
Small-molecule activation by low-valent main-group element compounds is of general interest. We here report the synthesis and characterization (1H, 13C, 29Si NMR, IR, sc-XRD) of heteroleptic metallasilylenes L1(Cl)MSiL2 (M=Al 1 , Ga 2 , L1=HC[C(Me)NDipp]2, Dipp=2,6-iPr2C6H3; L2=PhC(NtBu)2). Their electronic nature was analyzed by quantum chemical computations, while their promising potential in small-molecule activation was demonstrated in reactions with P4, which occurred with unprecedented [2+1+1] fragmentation of the P4 tetrahedron and formation of L1(Cl)MPSi(L2)PPSi(L2)PM(Cl)L1 (M=Al 3 , Ga 4 ). 相似文献
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