Reactions of cis-2-Boryl-1-stannylalkenes with Carbodiimides, Thiocyanates, Isothiocyanates, and Isocyanates |
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Authors: | B Wrackmeyer H E Maisel K Wagner |
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Institution: | (1) Laboratorium für Anorganische Chemie, Universität Bayreuth, D-95440 Bayreuth, Germany |
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Abstract: | The reactions of (E)-2-diethylboryl-1-trimethylstannylbut-1-ene and (Z)-3-diethylboryl-2-trimethylstannylpent-2-ene with carbodiimides, methyl thiocyanate, thioisocyanates, and isocyanates were studied, and the products were characterized by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C and 119Sn NMR). It was found that carbodiimides bearing tert-butyl or trimethylsilyl groups at the nitrogen atoms do not react with (E)-2-boryl-1-stannylalkenes, in contrast to dicyclohexylcarbodiimide. There was also no reaction in the case of MeSCN. All other reactions proceed via a weak N B adduct formation in the initial step, followed by different rearrangements, depending on the structure of reagents as well as on the substitution pattern at the C=C bond in alkenes. New heterocycles are formed, in which the boron atom is either tricoordinated (1,2-azaborolenes, 1,2-azaborolan! es), a nd one ethyl group has been transferred to the neighbor olefinic carbon atom, or the boron atom is tetracoordinated (1,2-azaboratoles, 1,2-oxoniaboratoles), and the trimethylstannyl group has migrated to one of the heteroatoms of the heterocumulenes. |
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Keywords: | (E)-2-diethylboryl-1-trimethylstannylbut-1-ene (Z)-3-diethylboryl-2-trimethylstannylpent-2-ene dicyclohexylcarbodiimide methylthiocyanate thioisocyanates isocyanates 1 2-azaborolenes 1 2-azaborolanes 1 2-azaboratoles 1 2-oxoniaboratoles |
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