Die Borierung von Lactamen und Harnstoffen mit einem Amino‐imino‐boran

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Abstract
Contribution to the Chemistry of Boron, 201. ‐ Boration of Lactams and Ureas by an Amino‐Imino‐BoranePyrrolidon reacts with (tert‐butylimino)(2,2,6,6‐tetramethylpiperidino)borane (1) to give the N‐borated lactam 2. Diketopiperazine behaves similarly. It is borated on both of its N atoms to form 3. Urea and 1 give access to the O,N,N′‐triborated isourea derivative 4, which contains the structural unit of a ketiminoborane. The diborated carbodiimide 10 is ultimately obtained from 1 and thiourea via the triborated isothiourea derivative 9. MNDO calculations have been used to estimate the relative thermodynamic stabilities of O/N borotropes of carbonic acid amides and lactams. They demonstrate that the O isomers gain in stability by increasing the size of N substituents.

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