Activation of Isocyanates and Carbon Dioxide by a Monomeric Aluminium Hydrazide as an Active Lewis Pair |
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Authors: | Dipl.‐Chem. Frank Hengesbach Dipl.‐Chem. Xing Jin Dr. Alexander Hepp Birgit Wibbeling Prof. Dr. Ernst‐Ulrich Würthwein Prof. Dr. Werner Uhl |
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Affiliation: | 1. Institut für Anorganische und Analytische Chemie der Universit?t Münster, Corrensstrasse 30, 48149 Münster (Germany);2. Organisch‐Chemisches Institut der Universit?t Münster, Corrensstrasse 40, 48149 Münster (Germany) |
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Abstract: | The monomeric aluminium hydrazide H10C5N? N(AltBu2)? Ad ( 4 ; Ad=adamantyl, NC5H10=piperidinyl) was obtained in high yield by hydroalumination of the corresponding hydrazone derivative 1 . Compound 4 has a strained AlN2 heterocycle formed by a donor–acceptor bond between the β‐nitrogen atom of the hydrazide group and the aluminium atom. Opening of this bond resulted in the formation of an active Lewis pair that was able to cooperatively activate carbon dioxide or isocyanates. Insertion of the heterocumulenes into the Al? N bond selectively afforded a carbamate and two urea derivatives in high yield. In the first step, phenyl isocyanate gave the adduct 6 , which has the oxygen atom coordinated to the aluminium atom and its central carbon atom bound to the nitrogen atom of the piperidine moiety. Adduct 6 represents a reasonable intermediate state for these activation processes. The applicability of hydroaluminated compounds, such as 4 , in organic synthesis was demonstrated by the reaction with an imidoyl chloride, which gave the corresponding amidrazone derivative 9 . |
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Keywords: | activation aluminium carbon dioxide hydrazines isocyanates |
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