1082608-29-4

Upstream product

• 462-06-6 fluorobenzene 
• 948054-44-2 lithium 1,3-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaborol-2-ide 
• 71-43-2 benzene 
• 591-51-5 phenyllithium 
• 98-88-4 benzoyl chloride 
• 727722-32-9 bromo(phenyl)(1,2-bis(diphenylphosphino)benzene)palladium 
• 108-86-1 bromobenzene 
• 1082608-12-5 C₂H₂N₂BI(2,6-(iPr)2C₆H₃)2 
• 915703-81-0 N,N'-bis(2,6-diisopropylphenyl)-2-bromo-2,3-dihydro-1H-1,3,2-diazaborole 
• 1008748-17-1 N,N'-bis(2,6-diisopropylphenyl)-2-chloro-1,3,2-diazaborole 
• 134750-23-5 N,N'-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene 

Relevant academic research and scientific papers

Catalytic Borylation using an Air-Stable Zinc Boryl Reagent: Systematic Access to Elusive Acylboranes

The use of borylzinc reagents in palladium-catalyzed borylation chemistry is described (i.e. a boron analogue of the Negishi coupling), including a one-pot bench-top protocol using an air- and moisture-stable bis(boryl)zinc reagent. The steric/electronic properties of the boryl fragment employed enable a systematic method for accessing acylboranes, a rare class of organoboron species with great potential in chemical synthesis. The reactions proceed under mild conditions, use inexpensive commercial sources of palladium, and demonstrate a remarkable functional-group tolerance.

Borylated N-Heterocyclic Carbenes: Rearrangement and Chemical Trapping

This study details attempts to access N-heterocyclic carbenes (NHCs) featuring the diazaborolyl group, {(HCNDipp)2B}, as one or both of the N-bound substituents, to generate strongly electron-donating and sterically imposing new carbene ligands. Attempts to isolate N-heterocyclic carbenes based around imidazolylidene or related heterocycles, are characterized by facile N-to-C migration of the boryl substituent. In the cases of imidazolium precursors bearing one N-bound diazaborolyl group and one methyl substituent, deprotonation leads to the generation of the target carbenes, which can be characterized in situ by NMR measurements, and trapped by reactions with metal fragments and elemental selenium. The half-lives of the free carbenes at room temperature range from 4–50 h (depending on the pattern of ancillary substituents) with N-to-C2 migration of the boryl function being shown to be the predominant rearrangement pathway. Kinetic studies show this to be a first-order process that occurs with an entropy of activation close to zero. DFT calculations imply that an intramolecular 1,2-shift is mechanistically feasible, with calculated activation energies of the order of 90–100 kJ mol?1, reflecting the retention of significant aromatic character in the imidazole ring in the transition state. Trapping of the carbene allows for evaluation of steric and electronic properties through systems of the type LAuCl, LRh(CO)2Cl, and LSe. A highly unsymmetrical (but nonetheless bulky) steric profile and moderately enhanced σ-donor capabilities (compared with IMes) are revealed.

Approaching a “Naked” Boryl Anion: Amide Metathesis as a Route to Calcium, Strontium, and Potassium Boryl Complexes

Amide metathesis has been used to generate the first structurally characterized boryl complexes of calcium and strontium, {(Me3Si)2N}M{B(NDippCH)2}(thf)n (M=Ca, n=2; M=Sr, n=3), through the reactions of the corresponding bis(amides), M{N(SiMe3)2}2(thf)2, with (thf)2Li- {B(NDippCH)2}. Most notably, this approach can also be applied to the analogous potassium amide K{N(SiMe3)2}, leading to the formation of the solvent-free borylpotassium dimer [K{B(NDippCH)2}]2, which is stable in the solid state at room temperature for extended periods (48 h). A dimeric structure has been determined crystallographically in which the K+ cations interact weakly with both the ipso-carbons of the flanking Dipp groups and the boron centres of the diazaborolyl heterocycles, with K???B distances of >3.1 ?. These structural features, together with atoms in molecules (QTAIM) calculations imply that the boron-containing fragment closely approaches a limiting description as a “free” boryl anion in the condensed phase.

A Combined Experimental/Computational Study of the Mechanism of a Palladium-Catalyzed Bora-Negishi Reaction

Experimental and computational efforts are reported which illuminate the mechanism of a novel boron version of the widespread Negishi coupling reaction that offers a new protocol for the formation of aryl/acyl C?B bonds using a bulky boryl fragment. The role of nucleophilic borylzinc reagents in the reduction of the PdII pre-catalysts to Pd0 active species has been demonstrated. The non-innocent behavior of the PPh3 ligands of the [Pd(PPh3)2Cl2] pre-catalyst under activation conditions has been probed both experimentally and computationally, revealing the formation of a trimetallic Pd species bearing bridging phosphide (PPh2?) ligands. Our studies also reveal the monoligated formulation of the Pd0 active species, which led us to synthesize related (η3-indenyl)Pd-monophosphine catalysts which show improved catalytic performances under mild conditions. A complete mechanistic proposal to aid future catalyst developments is provided.

Chemistry of boryllithium: Synthesis, structure, and reactivity

A series of lithium salts of boryl anion, boryllithiums, were synthesized and characterized by NMR spectroscopy and crystallographic analysis. In addition to the parent boryllithium compound 35a, structural modification of boryllithium, using saturated C-C and benzannulated C=C backbones in the five-membered ring and mesityl groups on the nitrogen atoms, also allowed generation of the corresponding boryllithium. The solid state structures of boryllithium showed that the boron-lithium bond is polarized where the boron atom is anionic in all (35a?DME)2, 35a?(THF)2, 35b?(THF)2, and 35c?(THF)2 when compared to the structures of hydroborane 38a-c and optimized free boryl anion opt-46a-c. Dissolution of the isolated single crystals of (35a?DME)2 and 35a?(THF)2 in THF-d8 showed that the boron-lithium bond remained in solution and free DME or THF molecules were observed. Temperature-dependent 11B NMR chemical shift changes of 35a were observed in THF-d8 or methylcyclohexane-d14, suggesting a change of chemical shift anisotropy around the boron center. The HOMO of opt-35a?(THF)2 had a lone pair character on the boron atom, as observed for phenyllithium, whereas the HOMO of hydroborane 38a corresponds to the π-orbital of the boron-containing five-membered heterocycle. The polarity of the B-Li bond, estimated by AIM analysis, was similar to that of alkyllithium. Boryllithiums 35a and 35b behave as a base or a boron nucleophile in reaction with organic electrophiles via deprotonation, SN2-type substitution, halogen-metal exchange or electron-transfer, 1,2-addition to a carbonyl group, and SNAr reaction. In the case of the reaction with CO2, intramolecular cyclization followed by CO elimination from borylcarboxylate anion and subsequent protonation gave hydroxyboranes 64a and 64b. The characters of the carbonyl groups in the borylcarbonyl compounds 60a, 60b, 61, 62, and 63a, which were obtained from the reaction of boryllithiums 35a and 35b, were investigated by X-ray crystallography, IR, and 13C NMR spectroscopy to show that the boryl substituent weakened the C=O bond when compared to carbon substituted analogues.