Klaus Beckerle  Ramanujachary Manivannan  Bing Lian  Geert‐Jan&#x;M. Meppelder  Gerhard Raabe  Thomas&#x;P. Spaniol  Henner Ebeling  Frederic Pelascini  Rolf Mülhaupt  Jun Okuda 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2007,119(25):4874-4877

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Frank Endres  Mirko Bukowski  Rolf Hempelmann  Harald Natter 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2003,115(29):3550-3552

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Huisgen R  Mloston G  Polborn K  Sustmann R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(10):2256-2263

The regiochemistry of 1,3-dithiolanes obtained from thiocarbonyl ylides 9 and thiones 10 shows a striking dependence on substituents. Previously and newly performed experiments indicate that sterically hindered cycloalkanethione S-methylides and dialkylthioketone S-methylides react with alicyclic and aliphatic thiones to give the 2,2,4,4-tetrasubstituted 1,3-dithiolanes 11 exclusively. Aryl groups in one or both reactants lead to a preference for, or even complete formation of, 4,4,5,5-tetrasubstituted 1,3-dithiolanes 12. Several mechanisms appear to be involved, but the paucity of experimental criteria is troubling. Quantum-chemical calculations (see preceding paper) on the cycloaddition between thioacetone S-methylide and thioacetone furnish lower activation energies for the concerted process than for the two-step pathways via C,S- or C,C-biradicals; the favoring of the 2,4-substituted 1,3-dithiolanes over the 4,5-substituted type would be expected to increase with growing bulk of substituents. Aryl groups stabilize intermediate biradicals. Experimental criteria for the differentiation of regioisomeric dithiolanes are discussed. Thiocarbonyl ylides 9 are prepared by 1,3-cycloadditions between diazomethane and thioketones and subsequent N(2) elimination from the usually isolable 2,5-dihydro-1,3,4-thiadiazoles 17; different ratios of the two rate constants lead to divergent product formation scenarios.  相似文献   

    

Dragan Pitzschke  Jing Wang  Rolf‐Dieter Hoffmann  Rainer Pttgen  Wolfgang Bensch 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2006,118(8):1327-1331

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Rolf W. Saalfrank  Christine Schmidt  Harald Maid  Frank Hampel  Walter Bauer  Andreas Scheurer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2006,118(2):322-325

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Bin Ren  Gennaro Picardi  Bruno Pettinger  Rolf Schuster  Gerhard Ertl 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2005,117(1):141-144

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Rolf Schiffmann  Andreas Heine  Gerhard Klebe  Christian D. P. Klein 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2005,117(23):3686-3689

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Klaus Bast  Matthias Behrens  Toni Durst  Rudolf Grashey  Rolf Huisgen  Reinhard Schiffer  Robert Temme 《European journal of organic chemistry》1998,1998(2):379-385

The red isoquinolinium N-arylimides 19−23 are azomethine imines of which the C=N bond is part of an aromatic ring. The N-(4-nitrophenyl)imide 22 and the N-(2-pyridyl)imide 23 were obtained crystalline; in solution the latter equilibrates with the hexahydrotetrazine 24 as its dimer. The N-phenylimide 19 is not stable; an isolated solid appears to be a tetramer. Generated by deprotonation of 11−13 , the N-arylimides 19−21 undergo in situ cycloadditions to carbon disulfide, phenyl isocyanate, phenyl isothiocyanate, and diphenylketene. The storable CS₂ adduct 29 offers a neutral source of theN-phenylimide 19 , since a cycloreversion equilibrium is established in solution.  相似文献   

    

Wolfgang R. Roth  Rolf Gleiter  Volker Paschmann  Ulrich E. Hackler  Gerd Fritzsche  Holger Lange 《European journal of organic chemistry》1998,1998(6):961-967

The observation of practically identical activation parameters for the Cope rearrangement 2 → 6 and its “frustrated” counterpart 1 → 5 indicates a two-step mechanism for the reaction 2 → 6 . Direct proof of this interpretation comes from trapping experiments, which demonstrate the intermediate formation of the diradicals 5 and 9 . From the temperature and oxygen dependences of the trapping rates, recombination barriers of ΔH^≠ = 11.5 and 6.5 kcal · mol⁻¹ have been derived for 5 → 1 and 9 → 6 , respectively. These results agree well with ab initio calculations (CASPT2).  相似文献   

    

Volker Wolfart  Rolf Gleiter  Hermann Irngartinger  Thomas Oeser  Claus Krieger 《European journal of organic chemistry》1998,1998(12):2803-2809

The synthesis of 1,8-diazacyclotetradeca-4,11-diyne ( 4 ) was accomplished by reaction of 1,6-dibromo-3-hexyne ( 11 ) with ammonia. Similarly, the preparation of 1-azacyclotetradeca-4,11-diyne ( 5 ) was achieved from 1,13-dibromotrideca-3,11-diyne ( 10 ) and ammonia. The reaction of α,ω-diamines of linear hydrocarbons of the chain length C₄ to C₁₀ with 11 yielded the corresponding bicyclic diynes 23-29 . The reaction of 4 with 11 yielded 1,8-diazabicyclo[6.6.6]icosa-4,11,16-triyne ( 14 ). Similarly, the reaction of 4 with 1,4-dibromo-2-butyne yielded 1,8-diazabicyclo[6.6.4]octadeca-4,11,16-triyne ( 31 ). The molecular structures of 1,8-diisopropyl-1,8-diazacyclotetradeca-4,11-diyne ( 13a ), as well as of 14 , 24 , 27 and 31 were studied by means of the X-ray technique. It was found that 13a adopts a chair-like conformation (C_2h) with an equatorial orientation of the isopropyl groups. In 14 , 24 , 27 , and 31 the 14-membered rings adopt a twist-boat conformation. The distance between the nitrogen atoms varies between 4.662(2) and 5.189(2) Å. In the case of 14 , 24 and 27 the nitrogen atoms are pyramidalized and point inside the cage while in 31 the substituents at each nitrogen atom and the nitrogen atoms are situated in one plane.  相似文献