Angewandte Chemie International Edition

Cover image for Vol. 55 Issue 27

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 (2012)

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.

  • 50 Years Ago...
    Angew. Chem. Int. Ed. 2012, 51, No. 49, 12148

    A series of Reviews dedicated to Otto Bayer on his 60th birthday reads like a “Who’s Who” of German chemistry at the time. The authors include Hans Meerwein et al., who wrote about ionic hydrogenations and dehydrogenations, Fritz Kröhnke et al., who discussed the synthesis of substituted pyridines by the Michael addition of pyridinium salts, and Siegfried Hünig et al., who outlined the synthesis of azo dyes by oxidative coupling. Otto Bayer founded the field of polyurethane chemistry and was Research Director of Bayer AG, but was not related to the Bayer family that founded the company. He was also on the Editorial Board of Angewandte Chemie. His contribution to chemistry is commemorated by the Otto Bayer Award (see Angew. Chem. Int. Ed. 2012, 51, 6310).

    The synthesis of oxazole was described by H. Bredereck and R. Bangert in a Communication. The route involved heating a hydroxyketosuccinic ester with formamide and reaction of the resulting di(alkoxycarbonyl)oxazole in situ to form oxazole. This procedure was reported to be relatively simple compared to that reported by Cornforth 15 years earlier.

    G. Manecke and W. Storck described how redox resins comprising cross-linked polymers of 2-vinyl-9,10-anthraquinone and styrene were obtained by thermal copolymerization in dimethyl sulfoxide with divinylbenzene as the cross-linking agent. The resins were pH-stable and had a very low redox potential

    Read more in Issue 12/1962

  • 50 Years Ago...
    Angew. Chem. Int. Ed. 2012, 51, No. 45, 11188

    Are the noble gases really inert? This question was answered 50 years ago with the synthesis of noble-gas compounds, and Rudolf Hoppe et al. reported the synthesis of XeF2 when a 1:2 mixture of purified Xe and F2 was subjected to an electric discharge in a sealed vessel. This report followed work reported in the same year by Neil Bartlett on XePtF6 and Howard H. Claasen on XeF4 and launched a new field of research, thus paving the way for classic chemistry textbooks to be rewritten. For a Review on the discovery of noble-gas compounds, see P. Laszlo, G. J. Schrobilgen, Angew. Chem. 1988, 100, 495; Angew. Chem. Int. Ed. Engl. 1988, 27, 479.

    The Review by R. Brill was on a “cool” topic: the structure of ice. Hydrogen bridges, disorder in the crystal structure, and mixed crystals were discussed in order to give an overview on the complex structure of such a well-known substance—a topic that is as “hot” today as it was 50 years ago.

    G. Wittig and D. Hellwinkel described the synthesis of bis(diphenylene)arylarsoranes. This synthesis, which involved the reaction of spirobis(diphenylene)arsonium salts, provides an alternative route to that reported by the same authors in Issue 1/1962.

    The complaints from workers in a veneer factory about skin irritation led W. Sandermann and M. H. Simatupang to investigate the active principle of teak wood. Analysis of golden yellow crystals that were deposited on teak veneers showed them to contain the toxic 2-γ,γ-dimethylallyl-1,4-naphthaquinone.

    Read more in Issue 11/1962

  • 50 Years Ago...
    Angew. Chem. Int. Ed. 2012, 51, No. 39, 9718

    Women in chemistry was a central topic of the International Year of Chemistry in 2011, and Issue 4/2011 was even dedicated entirely to this topic. 50 years ago, reports from female chemists were more rare, but still appeared in Angewandte Chemie: Margot Becke-Goehring and H. P. Latscha described the synthesis of the alkylated disulfur(IV) nitride [(CH3)2S-N=S(CH3)2]Cl. This compound was produced in 60 % yield from the reaction of trithiazyl chloride with dimethyl sulfoxide. Becke-Goehring, who was the mentor of the late Rolf Appel (see recent Obituary), was Rector of the University of Heidelberg and later Director of the Gmelin Institute for Inorganic Chemistry, which was responsible for publishing the Gmelin Handbook of Inorganic Chemistry.

    The synthesis of anionic heterosiloxanes was reported by Hubert Schmidbaur and Max Schmidt. They described how equimolar mixtures of [{(CH3)3SiO}3X]2 (X=Al or Ga) and MOSi(CH3)3 (M=Li, Na, or K) reacted in CCl4 to produce M[X{OSi(CH3)3}4]. Schmidbaur was later Chairman of the Editorial Board of Angewandte Chemie and an Essay by him on coordination chemistry at carbon is in press.

    The increasing popularity of organometallic chemistry was reflected in two Communications. Hans Bock discussed the synthesis of nickel(0) dialkylcyanamide carbonyls, which were formed by the reaction of dialkylcyanamides with an excess of Ni(CO)4. These compounds, which exist as orange crystals, comprise two nickel centers that are bridged by two carbonyl groups. Ernst Bayer et al. reported the synthesis of a ferrole dicarboxylic acid dimethyl ester tricarbonyl compound. Ferrole is a five-membered heterocycle that contains iron as the heteroatom and is formed by the elimination reaction of 1,4-dichlorobutadiene derivatives.

    Read more in Issue 10/1962

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2012, 51, No. 35, 8684

    Heteroatom chemistry was “in vogue”: The reactions of alkylboron compounds were the subject of two Communications in Issue 9/1962. R. Köster and G. Benedikt reported how the exchange reaction of B-ethylboraindane or B-ethylboratetralin with aluminum trialkyl compounds resulted in aluminum heterocycles. The products exist as dimers in solution and as colorless crystals in the solid state. P. Binger and R. Köster reported on the preparation and properties of cyclopropylboranes, and described how 1,1-bis- (dialkylboryl)-3-chloropropanes react with sodium tetraalkylboron compounds to form the desired products. Tricyclopropylborane was also prepared, and could undergo an exchange reaction with triethylaluminum to form cyclopropylaluminum species.

    The reaction of pyrilium salts with triphenylphosphine derivatives was reported to lead to substituted aromatic compounds. As described by G. Märkl, the initial reaction resulted in a ring opening to form a vinylogous phosphineacylmethylene compound, which then underwent an intramolecular Wittig reaction to form a substituted benzene derivative.

    F. Hübenett et al. reported on a simple synthesis of isothiazole ring systems, which were formed by passing propylene, ammonia, and sulfur dioxide over catalysts such as activated aluminum oxide. This method contrasts that reported in Issue 6/1962 by F. Wille et al., who reacted sodium acrolein 3-thiosulfate or acrolein 3-thiocyanate derivatives with liquid ammonia to produce isothiazole rings.

    Read more in Issue 9/1962

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2012, 51, No. 31, 7618

    Issue 8 in 1962 started with a Review by G. Wittig on small rings with carbon–carbon triple bonds, in particular the formation and reactions of benzyne (didehydrobenzene), which had been first postulated as intermediate by Wittig in 1942 and is still being exploited today. The issue of whether benzyne was a true intermediate or only a transition state was also addressed, and evidence that benzyne occurs as an intermediate in reactions, and in the gas phase was presented. A thermal synthesis of benzyne in a specially constructed apparatus led to its capture under high vacuum under argon, thus paving the way for further studies.

    The preparation of 5-amino sugars was discussed in by H. Paulsen in a Communication. These compounds are of particular interest as they can transform into piperidinoses, which comprise a six-membered ring that contains a nitrogen atom. The amino sugars were prepared as their acetamido derivatives, and upon hydrolysis, the carbonyl group interacts with the free amino group to produce a 3-hydroxypyridine after spontaneous elimination of water and aromatization of a postulated piperidinose intermediate.

    Angewandte Chemie has often published articles that use the results from further studies to dispute a previously reported claim, and a Communication by R. Huisgen and W. Edl opposed a statement made in 1927 that dibenzoyl peroxide can benzoxylate benzene in the presence of AlCl3. They reported that phenyl benzoate is in fact obtained in both toluene and non-aromatic solvents, and went on to describe how BF3 in dichloromethane is a particularly suitable catalyst for the production of carboxylic esters from mixed diacyl peroxides. A mechanism was proposed that was consistent with independent studies that used AlCl3 and an isotopically labeled peroxide, and were reported whilst the article was in press.

    Read more in Issue 8/1962

  • 50 Years Ago...
    Angew. Chem. Int. Ed. 2012, 51, No. 27, 6552

    Issue 7 in 1962 literally contained some explosive chemistry in the form of not one but two reports of unexpected explosions. H. Wilms and A. Dorlars described how they heated mesitylene with concentrated nitric acid in an autoclave. Several minutes after reaching 115°C and 10 atm gauge pressure, an explosion occurred that tore the autoclave apart lengthwise and ripped the steel doors from a safety cover. In a separate Communication, P. G. Ferrini and A. Marxer reported how tropylium perchlorate exploded when being manipulated with a glass rod. The explosion shattered the bench top, which broke the solvent bottles that were stored beneath it. The spilt solvent then caught fire. 50 years ago, reports such as this were a good way of making researchers more aware of the risks involved in these reactions, and thus helped to reduce the number of laboratory accidents.

    The ethylene ketal of cyclopentadienone was the subject of two back-to-back Communications that described different routes to this product. The approach reported by E. Vogel and E.-G. Wyes involved capturing the desired product as its maleic anhydride adduct, while C. H. DePuy, B. W. Ponder, and J. D. Fitzpatrick described how the dimer of the target compound was produced by elimination of a substituted cyclopentanone ketal.

    In a Review, U. Hofmann discussed the chemical basis of ancient Greek vase painting. A range of studies showed that illitic clay was used as a black paint and a kaolinitic clay was used as a red paint, and electron microscopy was used to examine the vase surfaces and elucidate the processes that occurred during the firing stage.

    Read more in Issue 7/1962

  • 50 Years Ago...
    Angew. Chem. Int. Ed. 2012, 51, No. 23, 5520

    Ferrocene was first reported over 60 years ago (see the forthcoming Essay by H. Werner, Angew. Chem. Int. Ed., in press), and by 1962, the chemistry of π complexes of aromatic compounds with transition metals was sufficiently mature that a Review on the subject was written by K. Plesske, who discussed the aromatic substitution reactions that these systems could undergo. Organometallic chemistry was also the subject of a Communication by W. H. Stubbs and P. L. Paulson, the latter of whom originally synthesized ferrocene, who reported on cyclopentadienyl metal isonitriles of manganese, iron, and nickel.

    Organic ring systems with adamantane-type structures were the subject of a Review and a Communication by H. Stetter. In the Review, ring systems such as oxa- and thia-adamantanes, as well as boric acid and metal complexes, were discussed, and results on the fragmentation of 3-bromoadamantane-1-carboxylic acid were reported in the Communication.

    The smells of onions and garlic are known to come from sulfur-containing compounds. In a Review, A. I. Virtanen summarized some of the organic sulfur compounds that can be isolated from onions and garlic, including the alkyl sulfide allicin from garlic, and the S-alkenyl-cysteine-S-oxide that is the precursor of the lachrymatory factor in onions. These active substances are formed only when the plant is crushed as the precursors and the enzymes that react with them are located in different cells.

    Read more in Issue 6/1962

  • 50 Years Ago...
    Angew. Chem. Int. Ed. 2012, 51, No. 19, 4508

    In the 1960s, mercurial diuretics—drugs that promote the formation of urine—were still the agents of choice if rapid action on the kidneys was required, however, given the toxicity of organomercury species, new orally active drugs were required. In a Review, E. Schlittler, G. Destevens, and L. Werner discussed the developments in non-mercurial diuretics, in particular the sulfonamide derivatives chlorothiazide and hydrochlorothiazide. In early 1961, hydrochlorothiazide was the leading product worldwide and the total sales for all non-mercurial diuretics in the USA was 45 million dollars—a large turnover in those days.

    Drug synthesis was also reported by U. Schmidt and F. Geiger, who discussed the total synthesis of the antibiotics thiolutin, aureothricin, and holomycin in a Communication. These antibiotics contain condensed pyrrolonedithiol ring systems and are active against pathogenic fungi and Gram-negative and Gram-positive bacteria.

    NMR spectroscopy was already beginning to have applications in physical chemistry, and W. Seiffert, H. Zimmermann, and G. Scheibe reported how the proton magnetic resonance spectra of aromatic heterocyclic compounds could be used for estimating π-electron densities in the molecular ground state. This estimation was carried out by comparing the chemical shifts of the molecule in question with those of benzene, and calculating the electron densities from these shift differences by using a calibration curve. The method was applied to pyridine and the experimentally derived values were comparable to those derived from quantum mechanical calculations.

    Read more in Issue 5/1962

  • 50 Years Ago...
    Angew. Chem. Int. Ed. 2012, 51, No. 13, 3042

    Already by Issue 4 in 1962, the new International Edition of Angewandte Chemie had started to attract contributions from all over the world. In a Communication from the former Czechoslovakia, J. Tomiška and E. Spousta reported the cleavage of the trioxane ring in acetic anhydride solution in the presence of strong mineral acids. The observed reaction was presumed to occur by a cationic cleavage of the ring followed by acylation of the resulting products. Acylated carbodiimides were the subject of two Communications from researchers in Chile, who discussed ring closures and elimination of hydrogen sulfide with these compounds.

    Fifty years ago, the measurement of chemical shifts was still relatively new, but the link between the effects measured by IR and NMR spectroscopy was already being explored. In a Communication, W. Seiffert reported the relationship between the C-H vibrational energy and the chemical shift of the protons in a series of substituted quinolines. A linear relation was found between the chemical shift of an isolated hydrogen atom in a ring and the deformation energy of its out-of-plane vibration.

    Side reactions can always be problematic, not least for H. Elsner and S. Saure, who reported an explosion during the uncatalyzed addition of trichlorobromomethane to ethylene in a high-pressure autoclave. Following three incident-free experiments, the autoclave exploded with great force, resulting in the autoclave and manometer being shattered and the laboratory walls to be covered in soot. It was assumed that a previously unknown side reaction had occurred.

    Enzymes were a common theme in the Reviews section, which contained articles on isozymes and heteroenzymes by Theodor Wieland and Gerhard Pfleiderer, and on microbial enzymes by Christoph Tamm. The latter Review discusses microbial transformations in natural products, including steroids, estrogens, and terpenes. These reactions were valuable in elucidating the biosynthesis and metabolism of the natural products.

    Read more in Issue 4/1962

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2012, 51, No. 09, 1992

    Fluorinated compounds have unique properties that are much exploited, and organofluorine compounds have several applications including heat-transfer agents, liquid crystals, dyes, surfactants, plastics, elastomers, and membranes. They are particularly important in the pharmaceutical and agrochemical industries. Fifty years ago however, fluoroalkyl compounds were relatively unknown, and a Review by H. J. Emeléus discussed the preparation and properties of trifluoroiodomethane, and the synthesis of fluoroalkyl derivatives of sulfur, nitrogen, and metallic elements. The Review closes with the prophetic lines “The subject has moved far and fast in the last twenty years and it is quite certain that we are not yet near the end of this fascinating journey.”

    What do hawthorn berries and the fruit of Gleditschia triacanthos, or the honey locust—a tree with long thorns—have in common? They both contain proanthocyanidins, which form anthocyanidins upon treatment with acid. In a Communication, K. Freudenberg and K. Weinges reported how the compound extracted from Gleditschia triacanthos fruit decomposed to form (+)-catechin and cyanidin. The proanthocyanidins were shown by hydrolysis and acetylation to contain a ketal linkage—something that could be very quickly proved today by using common spectroscopic techniques!

    Substance P is a neuropeptide comprising eleven amino acids. Since its first report in 1931, it has been extensively studied and has been since shown to be a neurotransmitter for pain receptors. H. Zuber and R. Jacques reported how substance P could be isolated from bovine brain by chromatography on Sephadex. 132 kg of bovine brain was required to isolate approximately 4 g of substance P.

    Read more in Issue 3/1962

  • 50 Years Ago...
    Angew. Chem. Int. Ed. 2012, 51, No. 05, 1092

    The Nobel Prize in Chemistry 1961 was awarded to M. Calvin for his “research on the carbon dioxide assimilation in plants”. Issue 2/1962 contains Calvin’s Nobel Lecture, in which he describes how 14C radiolabeling was used to track carbon that enters a plant as carbon dioxide and is turned to carbohydrate in the photosynthetic carbon cycle. Angewandte Chemie has kept the tradition of publishing the Nobel Lectures to this very day.

    These days, the mercury ion is considered an environmental hazard and its sensing and extraction are frequently reported. In former times however, HgSO4·2HgO, which was discovered in 1604, was even used medicinally! In 1962, A. Weiss reported on the structure of this salt, which was shown by X-ray studies to consist of polymeric (Hg3O2)+ cations in slightly undulating two-dimensional infinite layers.

    The butterfly and the salamander are the sources of natural products that were discussed in two Communications. C. Schöpf outlined how the pigment erythropterin was synthesized by treatment of xanthoperin with oxalacetic acid at pH 4.2 and 80°C. It was postulated that xanthoperin was the primary product in the biosynthesis of pteridine butterfly pigments. G. Habermehl reported the elucidation of the structure of samandaridine, which was isolated along with a range of other alkaloids from the skin gland venom of the fire and alpine salamanders. The structure was deduced from an X-ray study of the hydrobromide salt, and the configuration was confirmed by the two-dimensional electron density projection—quite an achievement 50 years ago!

    Read more in Issue 2/1962

  • 50 Years Ago ...
    Angew. Chem. Int. Ed. 2012, 51, No. 01, 22

    In 1962, Angewandte Chemie International Edition appeared 12 times per year but already published both Communications and Reviews across all areas of chemistry. The first issue of 1962 contains original contributions by some of today’s best-known names who had already made enormous contributions to their fields.

    The Ugi reaction is often the first that springs to mind if we are asked to name a multicomponent reaction today. This reaction was pioneered more than 50 years ago and in a Review, Ivar Ugi discussed his latest results in the one-stage synthesis of organic nitrogen compounds. The reactions, which started with two to five different components, proceed by the α-addition of immonium ions and anions to isonitriles, accompanied by secondary reactions.

    Another highly exploited reaction in modern organic chemistry is the 1,3-dipolar cycloaddition. This reaction was already being explored 50 years ago and the Communications section contains three contributions by Rolf Huisgen on the cycloaddition reaction of syndones with alkynes and alkenes, and 1,3-dipolar additions with nitrile ylides.

    The name of Georg Wittig (Nobel Prize in Chemistry 1979) is synonymous with organophosphorus chemistry, and he reported the synthesis of penta-aryl derivatives of Group 5 elements in a Communication that contained only 12 lines of text. This procedure was an improvement on the synthesis of phosphorane derivatives that could not be extended to the arsenic series.

    “A highly refractive red oil” was the product from the reaction of solid BaCS3 with ice-cold 10 % hydrochloric acid that was reported by Gerhard Gattow and Bernt Krebs. Characterization of this product by using the techniques available at the time, including cryoscopic molecular weight determination, IR spectroscopy, and decomposition analysis, showed it to be trithiocarbonic acid H2CS3.

    Read more in Issue 1/1962