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21.
L. Brandsma N. A. Nedolya O. A. Tarasova B. A. Trofimov 《Chemistry of Heterocyclic Compounds》2000,36(11):1241-1260
Novel syntheses of heterocyclic compounds resulting from reactions of metallated acetylenes, allenes, and conjugated dienes with isothiocyanates and from reactions of the latter with strong bases are reviewed. 相似文献
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Asymmetric Conjugate Additions and Allylic Alkylations Using Nucleophiles Generated by Hydro‐ or Carbometallation
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Dr. Rebecca M. Maksymowicz Andrew J. Bissette Dr. Stephen P. Fletcher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5668-5678
This Minireview discusses catalytic asymmetric conjugate addition and allylic alkylation reactions where the nucleophiles were generated in situ by hydrometallation or carbometallation. This exciting recent trend in asymmetric catalysis promises to expand the range of transformations available for the rapid and selective assembly of complex, functional molecules for both academic and industrial research. This Minireview aims to serve as a reference for studies reported to date and discusses the current state‐of‐the‐art, scope and limitations of these processes. 相似文献
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Dr. David R. Armstrong Jennifer A. Garden Dr. Alan R. Kennedy Sarah M. Leenhouts Prof. Robert E. Mulvey Philip O'Keefe Dr. Charles T. O'Hara Dr. Alan Steven 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(40):13492-13503
Most recent advances in metallation chemistry have centred on the bulky secondary amide 2,2,6,6‐tetramethylpiperidide (TMP) within mixed metal, often ate, compositions. However, the precursor amine TMP(H) is rather expensive so a cheaper substitute would be welcome. Thus this study was aimed towards developing cheaper non‐TMP based mixed‐metal bases and, as cis‐2,6‐dimethylpiperidide (cis‐DMP) was chosen as the alternative amide, developing cis‐DMP zincate chemistry which has received meagre attention compared to that of its methyl‐rich counterpart TMP. A new lithium diethylzincate, [(TMEDA)LiZn(cis‐DMP)Et2] (TMEDA=N,N,N′,N′‐tetramethylethylenediamine) has been synthesised by co‐complexation of Li(cis‐DMP), Et2Zn and TMEDA, and characterised by NMR (including DOSY) spectroscopy and X‐ray crystallography, which revealed a dinuclear contact ion pair arrangement. By using N,N‐diisopropylbenzamide as a test aromatic substrate, the deprotonative reactivity of [(TMEDA)LiZn(cis‐DMP)Et2] has been probed and contrasted with that of the known but previously uninvestigated di‐tert‐butylzincate, [(TMEDA)LiZn(cis‐DMP)tBu2]. The former was found to be the superior base (for example, producing the ortho‐deuteriated product in respective yields of 78 % and 48 % following D2O quenching of zincated benzamide intermediates). An 88 % yield of 2‐iodo‐N,N‐diisopropylbenzamide was obtained on reaction of two equivalents of the diethylzincate with the benzamide followed by iodination. Comparisons are also drawn using 1,1,1,3,3,3‐hexamethyldisilazide (HMDS), diisopropylamide and TMP as the amide component in the lithium amide, Et2Zn and TMEDA system. Under certain conditions, the cis‐DMP base system was found to give improved results in comparison to HMDS and diisopropylamide (DA), and comparable results to a TMP system. Two novel complexes isolated from reactions of the di‐tert‐butylzincate and crystallographically characterised, namely the pre‐metallation complex [{(iPr)2N(Ph)C?O}LiZn(cis‐DMP)tBu2] and the post‐metallation complex [(TMEDA)Li(cis‐DMP){2‐[1‐C(=O)N(iPr)2]C6H4}Zn(tBu)], shed valuable light on the structures and mechanisms involved in these alkali‐metal‐mediated zincation reactions. Aspects of these reactions are also modelled by DFT calculations. 相似文献
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α,α-Difluoroacylsilanes were synthesised directly from a range of allyl ethers of trifluoroethanol via dehydrofluorination/metallation procedures, followed by thermal [3,3]-sigmatropic rearrangement of the intermediate vinylmetals. The scope and limitations of ether synthesis and dehydrofluorination/metallation are described. 相似文献
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The pathway and degree of metallation of polymers were studied depending on the the conditions (temperature, concentration, nature, and component ratio) of metallation of poly(1-trimethylsilylprop-1-yne) (PTMSP) and poly(vinyltrimethylsilane) (PVTMS) by superbases, viz., BunLi and BusLi, in combination with potassium tert-pentyl oxide (PetOK). For the BunLi—PetOK system (1 : 3), the yield of modified PTMSP reached 90%. In the case of PTMSP, only the Me groups at the double bonds and at the Si atoms undergo metallation, whereas only the Me groups at the Si atoms are metallated in PVTMS. The kinetics of metallation with the BunLi—PetOK system was studied. 相似文献
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S. P. Gromov O. A. Fedorova A. I. Vedernikov V. V. Samoshin N. S. Zefirov M. V. Alfimov 《Russian Chemical Bulletin》1995,44(1):116-123
A method for the synthesis of 4-bromobenzodithia-15(18)-crown-5(6) and 4-bromobenzodiaza-15 (18)-crown-5(6) by condensation of 3,4-di(2-haloethoxy)bromobenzene with polyoxaalkanes containing terminal SH or NHMe groups was suggested. The method for the synthesis of formyl derivatives of benzocrowns containing N, S, and O heteroatoms in the macrocycle based on the metallation of appropriate bromo derivatives with BunLi followed by treatment of the resulting organolithium intermediates with DMF was developed. Oximes and semicarbazones of benzaldehydes containing a crown ether fragment were obtained, and their transformation into the original aldehydes by treatment with KNO2 in an acid medium was studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 121–128, January, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08-531) and the International Science Foundation (Grant M8Q000). 相似文献
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V. A. Nikanorov S. E. Mochalovskii A. Y. Komissarov S. V. Sergeev D. V. Zverev T. I. Strelkova E. V. Vorontsov P. V. Petrovskii 《Russian Chemical Bulletin》1996,45(8):1993-1995
Condensation of 4-methyl-4-trichloromethylcyclohexa-2,5-dienone with cyclopentadiene gave the first representative of cross-conjugated pentafulvenes of the para-semiquinoid series: 1-cyclopentadienylidene-4-methyl-4-trichloromethylcyclohexa-2,5-diene. This fulvene undergoes a novel redox aromatizational skeletal rearrangement under the action of (Ph3P)3Rh(CO)H and (C2H4)2Rh(acac) to give triphenylphosphinetn5-(p-tolylcyclopentadienyl)jdichlororhodium and bis[(5-p-tolylcyclopentadienyl)(w-chloro)chlororhodium], respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2098–2100, August, 1996. 相似文献
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V. A. Reznikov L. A. Vishnivetskaya L. B. Volodarskii 《Russian Chemical Bulletin》1993,42(9):1547-1551
Reactions of metallated 1-hydroxy-2,2,4,5,5-pentamethyl-3-imidazoline with electrophilic reagents followed by oxidation result in mono- and bifunctional substituted nitroxides of 3-imidazoline and an imidazolidine series including enaminocarbonyl and -thiocarbonyi derivatives and enaminoimines, the spin-labeled chelating reagents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1612–1616, September, 1993. 相似文献
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Maria Grazia CabidduSalvatore Cabiddu Enzo CadoniStefania De Montis Claudia FattuoniStefana Melis 《Tetrahedron》2003,59(16):2893-2897
The metallation reaction of N-Boc-and N-Piv-(methylthio)anilines are here described. The results show that N-Boc derivatives are metallated only by superbases to give products substituted at the thiomethylic group. N-Piv derivatives show a different behaviour: ortho-derivative is metallated by both butyllithium and superbase at the thiomethylic carbon atom, while para-derivative is metallated in ortho to the N-Piv group by butyllithium and at the thiomethylic carbon atom by superbase. The meta-derivative is metallated only by superbase at the thiomethylic carbon atom. 相似文献