Abstract

Contributions to the Chemistry of Boron, 2021). – Borylation of Amino Acids by an Amino‐imino‐borane Reactions of (tert‐butylimino)(2,2,6,6‐tetramethylpiperidino)‐borane (3) with amino acid esters or N,N‐dimethyl amino acids lead to the N‐borylated products 5 and boryl esters 11, respectively. Amino acids and 3 yield the O,N‐bis‐boryl compounds 13 and/or 1,3,2‐oxazaborolidin‐5‐ones 14, depending on the size of the organyl substituent R at the α‐carbon atom of the amino acid. Increasing the bulk of this group favours the formation of 14 with elimination of tert‐butylamine. The five‐membered OBNCC ring of 14 is planar according to an X‐ray structure analysis of 14e. (2,6‐Diisopropylphenylimino)(2,2,6,6‐tetramethylpiperidino)borane reacts with amino acids similar to 3, but tetramethylpiperidine is eliminated on ring formation to produce 20. N‐Monoalkyl amino acids and 3 predominantly give oxazaborolidin‐5‐ones.

Contribution to the Chemistry of Boron, 2011). -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 Reaktionen rnit LactamenIn Hexan reagiert 2-Pyrrolidon rasch rnit 1 im Molverhaltnis 1 : 1 nach G1. (1) zum Amido-bis(amino)-boran 2.Hinweise auf die Bildung des 0-Isomeren fanden sich nicht. Gleiches gilt fur die sehr langsam ablaufende Umsetzung mit 2,5-Diketopiperazin, die ausschlieI3lich zu 3 fuhrt. Grund hierfiir diirften die heterogenen Reaktionsbedingungen sein. Reaktionen rnit Harnstoff und ThioharnstoffObwohl Harnstoff in Hexan praktisch unloslich ist, setzt er sich relativ schnell rnit 1 nach G1. (2)

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/ Tetraborane(8), p-(tert-buty1imino)-p(tetramethylpiperidin0)-/ arachno-Undecaboranates( 13), -(organylamino)-1 1 -(tetramethylpiperidinio)-Contributions to the Chemistry of Boron, 213I'I. -Reactions of an Amino-imino-borane with Triborane(7) and Decaborane(l4)* Triborane(7)-THF hydroborates (tert-butylimino)(tetramethyl-ane/hexane solution. However, 1 reacts rapidly with piperidino)borane 1 slowly to form p-(fert-buty1amino)-p-(te-decaborane(l4) to produce a tetramethylpiperidine adduct of tramethylpiperidino)tetraborane(8) 5. This molecule shows an 11-(tert-butylamino)undecaborane( 14) as determined by an fluxional behaviour at ambient temperature in solution. In the X-ray structure analysis. The same kind of reaction occurs solid state, an X-ray structure analysis reveals the presence of between decaborane( 14) and (2,6-diisopropylphenylimino)-the asymmetric 1104-styx valence tautomer. 1 does not react (2,2,6,6-tetramethylpiperidino)borane. Thus, decaborane( 14) at ambient temperature with pentaborane(9) in dichlorometh-acts as a diprotic acid towards amino-imino-boranes.Die BN-Dreifachbindung von (tert-Butylimino)(2,2,6,6-tetramethy1piperidino)boran (1)