: Systemic Acquired Resistance (SAR) is an inducible resistance mechanism in plants that, together with other defence mechanisms, provides broadspectrum and long-lasting disease control. With novel screening techniques the benzo[1,2,3]thiadiazole-7-carboxylic acid derivatives have been identiÐed as a new class of chemicals which stimulate the plantÏs own defence mechanisms. The synthesis and biological activities of various benzo[1,2,3]thiadiazoles and related structures are described. S-Methyl benzo[1,2,3]thiadiazole-7-carbothioate is the Ðrst synthetic chemical "plant activatorÏ that has been developed for this novel disease control concept.
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ZUSCHRIFTEN A. M. Braun, M. Gratzel, noch unveroffentlicht. [SO] A. M. Braun, G. NuOberger, H. J. Poschel in J. Cornelisse: Organic Photochemical Synthesis. Vol. 3. in Vorbereitung.[51] a) M. P. Pileni, A. M. Braun, M. Gratzel, Photochem. Photobiol. 31, 423 (1980); b) M. Krieg, M. P. Pileni, A. M. Braun, M. Grurzel, noch unveroffentlicht. [56] Y Moroi, E. Promauro, M. Griitzel, E. Pelizzetti. P. Tundo, J . Colloid Interface Sci. 64, 341 (1974). [57] Komplexierung von Metallionen durch Aza-Kronenether siehe a) J. M. Lehn, J. P. Sauuage. B. Dietrich, J. Am. Chem. SOC. 92.291611970); b) H. K. Frensdod, ibid. 93, 600 (1971). [581 R. Humphry-Baker. M. Gratzel, P. Tundo, E. Pelizzetti, Angew. Chem. 91, 669 (1979); Angew. Chem. Int. Ed. Engl. 18,630 (1979). [59] S. A. Alkaitis, G. Beck, M. Griitzel. J. Am. Chem. SOC. 97, 5723 (1975). I601 S. A. Alkaitis, M. Gratzel. A. Henglein, Ber. Bunsenges. Phys. Chem. 79. 541 I611 S. A. Alkairis, M. Gratzel. J . Am. Chem. SOC. 98, 3549 (1976). [62] M. Krieg, A. M. Braun, R. Humphry-Baker, M. Cratzel, noch unveroffent-[63] P. A. Brugger, P. P. Infelta, A. M. Braun, M. Gratrel, J. Am. Chem. SOC., im [64] K. Kalyunasundaram, M. Griitzel, Angew. Chem. 91, 759 (1979); Angew. [65] J. Kiwi, E. Borgarello, E. Pelizzetti. M. Visca, M. Gratzel, Angew. Chem. 92. (1 977). (1975). licht. Druck. 734 0 Verlag Chemie, GmbH, D-6940 Weinheim. aquatoriale''] 4-Brom-1-azaadamantan (3a) fragmentieren quantitativ in 80% Ethanol zu den Methylenammoniumsal-Zen (7), (8) bzw. (9)[*]. Zudem reagieren sie ca. lo3-, lo4-bzw.105mal rascher als die stickstofffreien Stammverbindungen (4a), (5a) bzw. (6a). Dieser Vergleich zeigt die starke frangomere Beschleunigung der Ionisation von (la), (2a) und (3a)13]. Die Azabicyclen reagieren somit nach dem konzertierten Mechanismus, wie aufgrund der antiperiplanaren Anordnung der Bindung C(4)-R' und des Elektronenpaares an N(l) in bezug auf die Bindung C(2)-C(3) zu erwarten wad3].Das axiale"] Epimer (lb), in welchem diese stereoelektronische Bedingung nicht erfullt ist (vgl. l3I), reagiert dagegen langsamer als die Stammverbindung (4b), und zwar zu den Substitutions-und Eliminationsprodukten (lc) und (1 d) bzw. (12) neben dem Fragmentierungsprodukt (7). DaB sich (lb) funfmal langsamer umsetzt als (46) und daB mehrere Produkte entstehen, weist auf die kationische Zwischenstufe (10) hin, deren Bildung durch den elektronenziehenden induktiven (-I)-Effekt des Stickstoffatoms erschwert wird (SOH = Solvens).Uberraschenderweise reagiert das ebenfalls axiale"] Epimer (2b) zweimal, (3b) sogar 1230mal rascher als (56) bzw. (6a)['I, obwohl auch hier die stereoelektronischen Bedingungen fur eine konzertierte Fragmentierung nicht erfullt sind141. Bei (2b) und (36) wird auBer Fragmentierung zu (8) bzw. (9) auch Substitution zu (2c) bzw. (3c) und, im Falle von (Zb), Elimination zum Olefin (1 3) beobachtet; dies deutet auf die kationischen Zwischenstufen (11) bzw. (14) hin. Diese Annahme wird durch den Befimd gestutzt, daB Zugabe von zehn Aquiv. Natriumazid zu einer waBrigen Lo...
The preparation of CGA 80000 (a-[N-(3-chloro-2,6-xylyl)-2-methoxyacetamidol-y-butyrolactone) and the separation of the four optical isomers and the diastereomeric pairs of enantiomers are described. The relationships between their absolute configurations and fungicidal activities have been examined. Biological tests have proved that one of the four isomers, with the absolute configuration (as, 3R) is mainly responsible for the fungicidal activity of CGA 80000.is not a BSI/ISO approved common name.The name clozylacon has been used for this compound. This EXPERIMENTALAll new compounds have been fully characterised by NMR and elemental analysis. N M R spectra were recorded on a Bruker AM-300 instrument; chemical shifts are reported in ppm relative to internal tetramethylsilane standard (= 0 ppm). Melting points are uncorrected. Chemical synthesisThe preferred sequence for the preparation of CGA 80000 started from 2,6-dimethylaniline and involved three steps as shown in Fig. 2. 2.1.1 a-(2,6-Xylidino)-y-butyrolactone (Fig. 2 ; ZZZ) Anhydrous sodium carbonate (64 g; 0.6 mole) was suspended in a solution of 2,6-dimethylaniline (121 g; 1.0 mole) in xylene (500 ml). a-Bromo-y-butyrolactone (206 g; 1.25 mole) was added over a period of 2 h to this suspension at reflux temperature (about 140°C). After completion of the addition, the reaction mixture was stirred for 4 h at the same temperature. Water produced in the reaction was removed during the addition of the abromo-y-butyrolactone and during the subsequent stirring by means of a Dean and Stark trap. The reaction 223 Pesric. Sci.
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