Angewandte Chemie International Edition

Cover image for Vol. 54 Issue 49

Editor: Peter Gölitz, Deputy Editors: Neville Compton, Haymo Ross

Online ISSN: 1521-3773

Associated Title(s): Angewandte Chemie, Chemistry - A European Journal, Chemistry – An Asian Journal, ChemistryOpen, ChemPlusChem, Zeitschrift für Chemie

Flashback: 50 Years Ago

Angewandte Chemie International Edition was first published in 1962, the mother journal first in 1888. In this monthly flashback, we feature some of the articles that appeared 50 years ago. This look back can open our eyes, stimulate discussion, or even raise a smile.

Archive: 2014 2013 2012

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 44, 12840

    The preparation of new elements by bombarding samples with heavy ions was a field that had already taken off: neptunium (atomic number 93) was first reported in 1940, and elements with atomic numbers 102, 103, and 104 were reported in 1957, 1961, and 1964, respectively. In a Review, C. Keller discussed the synthesis of transcurium elements. He postulated “...the next few years may witness the discovery of isotopes of elements up to atomic number 109 ...”. He was certainly correct: element 109 (meitnerium) was first created in 1982.

    Hellmut Bredereck, Rolf Gleiter, and co-workers published two Communications. The first report was on the reactions of N,N-disubstituted formamides with alkali metals, which proceeded with the evolution of hydrogen to form the metal formamide. The salt then either decomposed with loss of carbon monoxide to form the metal dialkylamide, or reacted with the starting formamide to produce the salt of the substituted glyoxylamide. The second report described the reaction of N,N-dimethyl-3-dimethylaminoprop-1-enylideneammonium salts. Treatment with potassium methoxide resulted in the formation of N,N,N',N'-tetramethyl-1-propene-1,3-diamine, and treatment with sodium dimethylamide resulted in the formation of N,N,N',N',N'',N''-hexamethyl-3-propene-1,1,3-triamine. Reaction of these products with CH-acidic compounds resulted in the formation of butadiene derivatives.

    Adolf Krebs outlined the occurrence of 1,2-didehydrocyclooctatetraene as an intermediate in the reaction of bromocyclooctatetraene with potassium tert-butoxide. The presence of the intermediate was confirmed by identifying the products of trapping experiments.

    Read more in Issue 11/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 39, 11308

    A range of reviews showed just how important various spectroscopic techniques had become. H. T. Witt et al. discussed the use of flashlight techniques in the analysis of photosynthetic processes by studying the time variation of the absorption spectra of chloroplasts after excitation. A. Almenningen et al. outlined the theory of electron diffraction for the study of gas-phase molecules, L. Vellutz and M. Legrand discussed progress in optical circular dichroism, and F. Schneider et al. summarized the use of electron paramagnetic resonance in organic chemistry.

    The Communications section also contained contributions that featured spectroscopic techniques. T. Kruck and W. Lang reported on the synthesis of HIr(PF3)4 and on the NMR spectra of HM(PF3)4, where M=Co, Rh, Ir. Coupling with the 31P and 19F nuclei means that the proton signal should theoretically split into a multiplet containing 65 lines, although there was a degree of overlap of the signals. In another Communication, W. Lüttke and K. Wilhelm described how they used infrared spectroscopy to study methylenetriphenylphosphoranes. They concluded that the bond between the phosphorus and the methylene carbon atom has only a slight double-bond character, which is useful to know for understanding Wittig reaction.

    Angewandte Chemie has always published stimulating chemistry, not least the report by F. Korte et al. on the separation of hashish extract and the subsequent isolation and identification of tetrahydrocannabinolcarboxylic acid. At the time, this acid was regarded as the “missing link” in the biosynthetic pathway of the active principles of hashish.

    Read more in Issue 10/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 35, 10056

    1965 saw the 100th anniversary of Kekulé’s rationalization of the benzene ring structure. In a Review, Hermann Hartmann described the history of the benzene formula, including a discussion of Hückel’s theory of aromaticity. To mark the 150th anniversary, this journal published an Essay earlier this year by Alan Rocke that gives a comprehensive history of how Kekulé approached the problem (see Angew. Chem. Int. Ed. 2015, 54, 46).

    The structure of benzene was the subject of further Reviews: Georg Wittig discussed the generation and reactions of 1,2-didehydrobenzene, and Eugen E. van Tamalen and Heinz G. Viehe discussed valence-bond isomers of aromatic systems and substituted benzenes (such as Dewar benzene and prismane), respectively.

    Hans Bock reported on a new aromatic substitution reaction in the form of dialkylamination. The reaction of N-chlorodialkylamines with aromatic compounds could be achieved by heating or irradiating the reactants in sulfuric acid, or by heating with a Lewis acid catalyst. For Bock’s Obituary, see Angew. Chem. 2008, 47, 2912.

    Max Schmidt described the reactions of diphenylphosphinotriphenyltin with compounds such as CS2, COS, and CSCl2. The reactions were postulated to proceed by a four-centered concerted mechanism at the Sn-P bond.

    Read more in Issue 9/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 31, 8864

    The field of organic semiconducors is a hot topic today, and 50 years ago the area was already attracting some interest as scientists were keen to know whether organic compounds showed similar behavior to the better known inorganic semiconductors. In a Review, Hans Meier discussed the photoconduction properties of organic dyes, including n- and p-type conductivity. Polythiophenes, cyanine dyes, and phthalocyanine derivatives were among the compounds described.

    Carrying out experiments in liquid hydrogen fluoride is certainly not for the faint hearted, however studies on the reaction of liquid hydrogen fluoride (which is a stronger acid than its aqueous counterpart) with nitrous acid and its derivatives were indeed carried out, as outlined in a Review by Fritz Seel. The products of these reactions contained nitrosyl fluoride solvated by hydrogen fluoride, and are valuable reagents in fluorine chemistry.

    André S. Dreiding reported on a rearrangement of ar-tetralols. When 1,2,3,4,6,9-hexahydro-6-oxo-9-methylnaphthalene was heated with sulfuric acid, 8-methyl-5-tetralol was the major product, and when mineral acids were used then 5-methyl-7-tetralol was the major product. However, with 70 % perchloric acid, 7-methyl-5-tetralol was the sole product. The differences were ascribed to the reactions being either under kinetic or thermodynamic control. Dreiding was the founder of the famous Bürgenstock Conference, which celebrated its 50th anniversary this year (for more details see Angew. Chem. Int. Ed. 2015, 54, 5014).

    Ekkehart Winterfeldt published a Communication on the stereochemistry of the addition reactions to acetylenic triple bonds. Mechanistic studies showed that the cis adducts are produced by a cyclic electron shift, and contradicted previous claims that compounds with easily abstractable hydrogen atoms always undergo trans addition reactions. Winterfeldt’s Obituary can be read at Angew. Chem. Int. Ed. 2015, 54, 35.

    Read more in Issue 8/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 27, 7734

    Hetarynes (o-didehydroaromatic compounds with heteroatoms in the ring) were the topic of a Review by T. Kauffmann, who discussed the synthesis and properties of these compounds. In another Review article, K.-D. Gundermann outlined recent progress in the chemiluminescence of organic compounds, which was made easier by the development of sensitive equipment. Luminol firefly luciferin, and lucigenin were among the compounds discussed.

    E. G. Rochow and P. Geymayer reported on the synthesis of N,N'-bis(chlorodimethylsilyl)tetramethylcyclodisilazane, which was produced by the reaction of 1,3-dichlorotetramethyldisilazane with sodium bistrimethylsilylamide. The product was regarded as a potential starting material for polymer synthesis.

    G. Köbrich and H. Heinemann published a Communication on tri(isopropylidene)cyclopropane. The analogous trimethylenecyclopropane was predicted to polymerize in the solid state, however, the hexamethyl derivative could be prepared from the reaction of tetramethylbutatriene with α-bromo-β,β-dimethylvinyllithium and was found to be extremely stable.

    H.-P. Boehm et al. reported on the reaction of organolithium compounds with silicon dioxide upon heating the reactants in ether for around 8 hours. A range of products were formed from phenyllithium, including tetraphenylsilane, triphenylsilanol, and diphenylsilandiol; the reaction was thought to occur by a nucleophilic attack on surface siloxane bonds. Boehm was one of the first to report the synthesis and characterization of graphene films (for his personal account see Angew. Chem. Int. Ed. 2010, 49, 9332)..

    Read more in Issue 7/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 23, 6666

    Ivar Ugi is today best known for the multicomponent reaction that bears his name. In a Review, he summarized various routes for the synthesis of isonitriles (now known as isocyanides according to the IUPAC rules); the most efficient method for the preparation of large quantities of isonitriles was the reaction of phosgene with tertiary amines. In another Review, Hans Bock discussed the synthesis and spectroscopic characterization of azo compounds in order to establish the relationship between the color and constitution of the derivatives. It was found that varying the substituents caused shifts in the n[RIGHTWARDS ARROW]π* transition. Interestingly, this was one of the first articles in Angewandte Chemie to contain color figures.

    Hellmut Bredereck et al. published two Communications on the subject of acetals. The first report addressed the reactions of dimethylformamide acetals with isothiocyanates. Depending on the substituents, either 1,3-disubstituted 2,4-dithioxoparabanic O,N-acetals or α-substituted imino-α-(ethylthio)dimethylacetamides were formed. In the second Communication, the reactions of amide acetals with hydrocyanic acid were reported; O,N-acetals of α-ketonitriles were produced in good yields. Bredereck was President of the Gesellschaft Deutscher Chemiker (GDCh; German Chemical Society) in 1968/1969.

    Christian Reichardt reported on the synthesis and spectroscopic properties of γ-phenylazopentamethinecyanine dyes. Introduction of the phenylazo group led to a hypsochromic shift of the long-wavelength bands. Reichardt is the author of Solvent Effects in Organic Chemistry, which was first published by Verlag Chemie in 1969, and the fourth edition of this truly classic text (published by Wiley-VCH and with Thomas Welton as co-author) appeared in 2011.

    Read more in Issue 6/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 19, 5544

    The use of mass spectrometry for the analysis of organic compounds was in its infancy but was already being explored by pioneers such as McLafferty and Djerassi. In a Review, Gerhard Spiteller and Margot Spiteller-Friedmann discuss structural elucidation of organic compounds by analysis of the fragmentation products.

    Horst Prinzbach et al. reported on the photochemical isomerization of exo-tricyclo[,4]octene derivatives to form tetracyclo[,8.04,6]octane compounds. Various derivatives were investigated, and carboxylic acids were found to isomerize more efficiently than esters. Prinzbach’s many achievements were summarized in his Obituary (see Angew. Chem. Int. Ed. 2012, 51, 11936).

    In another Communication, Prinzbach and Arthur Lüttringhaus discussed the proton activity of 1,3-dithiolium cations. NMR spectroscopy was used to measure the half-lives of hydrogen–deuterium exchange at the 2-position. The cations were reacted further to produce tetrathiafulvalene derivatives, the mass spectra of which showed a peak corresponding to the resulting dithiacarbene fragment. Together with Gottfried Schill, Lüttringhaus reported the first templated synthesis of a catenane (for the full story see the Editorial by J. Fraser Stoddart in Angew. Chem. Int. Ed. 2014, 53, 11102).

    H. J. Berthold and H. Knecht published two Communications on the reactions of uranium trichloride and tetrachloride. The first report outlined the reactions of UCl3 and UCl4 with liquid ammonia at low temperature to produce ammoniates with the compositions UCl3·(6.8–6.9)NH3 and UCl4·(7.3–7.5)NH3. In the second Communication, the high-temperature reaction was discussed, and compounds such as UNH2Cl2, U(NH2)2Cl, and UNH2Cl3 were found to be formed.

    Read more in Issue 5/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 13, 3846

    2015 sees the 150th anniversary of BASF, and Issue 11/2015 of Angewandte Chemie was dedicated to this jubilee. For the 100th anniversary in 1965, Angewandte Chemie also published a series of Reviews dedicated to the company, then called the Badische Anilin- & Soda-Fabrik. These included contributions by Siegfried Hünig et al. on the chemistry of diimine (N2H2), and by Ralph G. Pearson and Mary M. Anderson on the exchange rates of ligands in complex ions. Pearson is best known for his work on hard and soft acids and bases, which he first published in 1963. Contributions from BASF included Reviews on cotton dyes (H. R. Hensel and G. Lützel), metal chelates as polymerization initiators (E.-G. Kastning et al.), the catalytic oligomerization of butene (H. Müller et al.), fungicidal compounds (K.-H. König et al.), catalysts for the synthesis of ammonia (R. Krabetz and C. Peters), and the latest technological developments in “mechanizing” the storage of chemical documentation (E. Meyer).

    Emanuel Vogel et al. reported on the synthesis of the bicyclo[5.4.1.]dodecapentaenylium ion. Reaction of 1,6-methanocyclodecapentaene with diazomethane and treatment of the resulting olefin with triphenylmethyl fluoroborate resulted in the target product, which is an arenium ion with 10 π electrons.

    K. Pilgram and F. Korte reported on the synthesis of the highly explosive bis(1,2,3,4-thiatriazol)thio compounds from sodium 1,2,3,4-thiatriazol-5-thiolate. These compounds were found to be stable at room temperature but exploded with a loud bang upon striking.

    Read more in Issue 4/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 09, 2578

    The chemistry of heterosiloxanes was the subject of a Review by Hubert Schmidbaur, a former Chairman of the Editorial Board of Angewandte Chemie. 50 years later, at the age of 80, Schmidbaur is still actively publishing; his Review on argentophilic interactions appeared in a very recent issue (see Angew. Chem. Int. Ed. 2015, 54, 746).

    Ernst Otto Fischer, who shared the 1973 Nobel Prize in Chemistry with Geoffrey Wilkinson, reported on isonitrilocyclopentadienyl complexes of lanthanoids. These complexes were formed by the reaction of lanthanoid tricyclopentadienyl complexes with cyclohexyl isonitrile, and were the first reported examples of compounds where a stable metal–carbon σ bond is formed for rare-earth metals.

    Armin Weiss et al. reported on the crystal structure of strontium disilicide. The silicon atoms were found to form a three-dimensional network with Si–Si distances comparable to that of elemental silicon. This structure contrasts with those other disilicides that contain two-dimensional nets or isolated tetrahedra of silicon atoms.

    Horst Prinzbach et al. published two Communications on conjugated π-bond systems. The first report described the synthesis of a monobenzo derivative of cyclopropenylidenecyclopentadiene (calicene), which is a highly strained but also delocalized system. Interestingly, a report from Andrew S. Kende on a similar calicene derivative was published shortly afterwards (J. Am. Chem. Soc. 1965, 87, 1609). Prinzbach’s second contribution was on stable methylenephenalene derivatives (phenalenes are three fused six-membered rings). Prinzbach was one of the most influential German organic chemists in the latter half of the last century, and was famous for the synthesis of a range of nonbenzenoid organic compounds, including dodecahedrane (for more details see his Obituary: Angew. Chem. 2012, 51, 11936).

    Read more in Issue 3/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 05, 1388

    Giulio Natta, who shared the 1963 Nobel Prize in Chemistry with Karl Ziegler, contributed a Review on the analogies between the stereochemical properties of macromolecules and those of classic organic cyclic compounds. In another Review, Dieter Seebach discussed the properties of three- and four-membered polycyclic systems, in particular tetrahedrane, Dewar benzene, prismane, and cubane. Seebach published a Minireview on geminal disubstitution in the 50th Jubilee Issue of Angewandte Chemie International Edition (see Angew. Chem. Int. Ed. 2014, 50, 96).

    Hubert Schmidbaur (former Chairman of the Editorial Board of Angewandte Chemie) contributed three Communications on gallium-containing compounds. The first was on the synthesis of dichlorogallane HGaCl2 , which was formed by the reaction of trimethylsilane with gallium trichloride. The second report was on organoheterosilanes Me3SiOXMe2 and Me3COXMe2 (X=Al, Ga, or In), which occur as dimers that have a four-membered ring structure, and the third on the synthesis of trimethylaluminum trimethylphosphorus oxide and trimethylarsenic trimethylgallium oxide. Schmidbaur’s Review on argentophilic interactions is currently in press (see Angew. Chem. Int. Ed. 2014, DOI: 10.1002/anie.201405936).

    Hermann Stetter, after whom the Stetter reaction was named, described a new synthesis of the adamantane derivatives substituted in the 3-position, which were constructed by the cyclization of 3-methylenebicyclo[3.3.1]nonan-7-one or 3,7-dimethylenebicyclo[3.3.1]nonane in the presence of acids. This method could also be used to synthesize adamantane-containing polymers.

    Read more in Issue 5/1965.

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2015, 54, No. 01, 22

    Richard Kuhn et al. reported on the stable triradical 1,3,5-tris-(1,5-diphenylverdazyl-3-yl)benzene, which contains ten conjugated six-membered rings and three unpaired electrons per molecule. Paramagnetic susceptibility and EPR measurements were used to confirm the radical nature of the compound, and it was noted that, unlike related biradicals, its electron spin remained unchanged down to 77 K.

    Klaus Hafner et al. discussed the synthesis of pentaleno[2,1,6-def]heptalene. This molecule is a nonbenzenoid isomer of pyrene and can be described as either two pentalene and two heptalene units, or two azulene systems. The compound was of interest for investigating the connection between structure and aromaticity, however it was found that, despite its 4n π electrons, the compound was inert toward electrophilic reagents.

    The issue also contained several Reviews on, at that time, contemporary topics in organic chemistry. Wolfgang Kirmse summarized the current knowledge of the intermediates of α-elimination reactions, including a discussion of radical and organometallic (carbanion) intermediates; Adolf W. Krebs discussed the properties of cyclopropenium compounds and cyclopropenones, which are Hückel aromatic (4n+2) π-electron systems; and Gert Köbrich detailed the various possible mechanisms of elimination reactions from olefins.

    Read more in Issue 1/1965.