1992 cycloaddition reactions cycloaddition reactions O 0070
-066Dipolar Cycloaddition Reactions of Organic Bisazides with Some Acetylenic Compounds.-(I) as well as its meta and para isomer react with the acetylenedicarboxylates (II) to give (III)-(V) in high yields. The reaction of the three bisazides with (VI) leads to a mixture of two isomeric compounds, as shown for the example of the ortho derivative ( I). From steric and statistical considerations (VII) is supposed to be the major product. In contrast to these results, the reaction of (I) with ethyl propiolate proceeds with complete regiospecificity to give ( X). The meta and para analogues of (I) react analogously. -(ABU-ORABI, S.; ATFAH, A.; JIBRIL, I.; MARII, F.; ALI, A. A.-S.; Gazz.
Dimethylphenol durch Veresterung und intramolekulare Arylkupplung synthetisieren l a~s e n [~~. Die Ergebnisse der Ringoffnungsexperimente sind in Tabelle 1 zusammengefaat.Die Leistungsfahigkeit des Verfahrens zeigt sich in den schon mit den monocyclischen Derivaten 3a-c erzielten guten Ergebnissen, vor allem aber in den zum Teil exzellenten Atropisomerenverhaltnissen mit den bicyclischen Reagentien 4a-c, die bei praktisch quantitativem Umsatz durchweg bei mindestens 90: 10 liegen. Dabei wurden die mit Abstand hochsten asymmetrischen Induktionen, unabhangig vom verwendeten Lacton, rnit den B-Methyl-und B-n-Butyl-Derivaten 4b und 4c erhalten.
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