REDUCTION OF PIPERIDINO- AND RELATED SEC.AMINO (DIHALOGENO)BORANES WITH LiAIH4 IN TOLUENE AND RELATED REACTIONS

Abstract

The products of the reduction of dihalogeno(diorganylamino)boranes with LiAIHj in toluene depend upon the steric requirement of the aminosubstituents.' It shows that upon using different procedures to produce sec.amino(dihydro)boranes the results depend critically from the solvent, the stoichiometry of the educts and the temperature applied beyond the sterical factors. However, certain procedures are preferably used to produce distinct moieties. Eight procedures (in part using different ratios of the educts) were applied and evaluated for their results. Mixtures of products were explored by NMR and MS. Pure compounds are characterized by NMR: Η, Β, C, MS and elemental analyses or high resolution MS. An X-ray structure analysis is presented for 26b.

Stoichiometric and Catalytic Reactivity of tert-Butylamine–Borane with Calcium Silylamides

“…65,66 . 26,39,[73][74][75] The formation of borohydride species during this reaction was also confirmed by a further single crystal X-ray diffraction analysis. Although the crystals diffracted weakly at high angles, leading to consequentially high residuals, the connectivity of the inorganic calcium tetrahydroborate (5) was unambiguous (Figure 4).…”

“…Compound 4 is the cycloborazane species [ t- BuHN–BH 2 ] 2 and, as such, is the first crystallographically characterized cyclodimeric product of a dehydrogenated primary amine–borane to be described. All previously reported products for transition-metal-catalyzed dehydrocoupling of primary amine–boranes have comprised higher oligomers, ,,,, while all six crystallographically characterized species of similar N 2 B 2 structure ( IX – XIV , Figure ), ,,− are compounds containing secondary amine derived units. The B–N bond distances (1.599(3) and 1.600(3) Å) in the solid-state structure of 4 are identical with those reported for IX (1.594(4) Å), , X (four in the unit cell in the range 1.584(5)–1.609(5) Å), XI (1.600 Å), XII (1.616 Å), and XIII (1.594(4) Å) but are shorter in comparison to that of XIV (1.621 Å), which possesses more sterically demanding 2,6-dimethylpiperidinyl nitrogen-centered substituents …”

Monomeric (dialkylamino)boranes: a new and efficient boron source in palladium catalyzed C–B bond formation with aryl halides

“…(Amino)dihydroboranes readily form mixtures of cyclic and linear oligomers 3 that often prevent any purification. Provided that the nitrogen atom is hindered enough, they can be obtained in their monomeric form by tedious reduction of corresponding (amino)dihaloboranes 4 or via the under-used thermally-induced dehydrogenation 5 of chosen secondary amine-borane adducts. We then revisited this thermal decomposition considering the incidence of steric hindrance on the physical properties of the final product in order to define the best monomeric candidates, including a chiral version 6 for further synthetic purposes.…”

Aminoboranes via Tandem Iodination/Dehydroiodination for One-Pot Borylation

“…(i)]. 14 Large-scale synthesis of aminoboranes using this protocol is limited by the highly reactive nature of the hydride and boron halide reagents. This method has since been supplanted by the thermal dehydrogenation of amine-boranes [ Scheme 1 .…”