2,7-Carbazole Derived Organoboron Compounds: Synthesis and Molecular Fluorescence

Triarylboranes have drawn much attention in OLEDs owing to their remarkable solid-state luminescence properties. Here two new A-D-A type compounds, 2,7-bis(dimesitylboryl)-N-ethyl-carbazole (BCz) using triarylborane as electron acceptor and carbazole as electron donor while 2,7-bis((4-(dimesitylboryl)phenyl)ethynyl)-9-ethyl-carbazole (BPACz) using phenylacetylene as extra conjugated bridge, have been synthesized and their photoluminescence related properties in various states have been investigated both experimentally and theoretically. Both compounds show blue emission with high quantum yields, being potential candidates for blue OLED materials.

Synthesizing highly fluorinated oligophenyls via Negishi coupling of fluoroarylzinc pivalates

Previously established general synthetic methods for the synthesis of highly fluorinated biphenyls using Suzuki-Miyaura protocols require the use of organoboron compounds which are not very stable under reactions conditions and thus need to be used in large excess. Herein we report an improved general strategy for the synthesis of highly fluorinated biphenyls, terphenyls and phenyl-substituted terphenyls using organozinc pivalates. The influence of several parameters was investigated: a) in a series of different monodentate phosphine ligands, X-Phos showed the best performance; b) a higher yield could be obtained for substrates bearing less steric hindrance or lower amount of fluorine substitution; c) as iodinated substrates decomposed during the reaction, brominated electrophiles were found to be superior. The presented protocol is scalable, versatile, and works with commonly used and commercially available phosphine ligands (X Phos) and palladium sources (Pd2dba3). Also, it does not need excess nucleophile usage for terphenyl synthesis and only a slight such excess for the preparation of phenyl substituted terphenyls.

A unified synthetic strategy to introduce heteroatoms via electrochemical functionalization of alkyl organoboron reagents

Based on systematic electrochemical analyses, an integrated synthetic platform of C(sp3)-based organoboron compounds was established for the introduction of heteroatoms. The electrochemically mediated bond-forming strategy was shown to be highly effective for the functionalization of sp3-hybridized carbon atoms with significant steric hindrance. Moreover, virtually all the nonmetallic heteroatoms could be utilized as reaction partners using one unified protocol. The observed reactivity stems from the two consecutive single-electron oxidations of the substrate, which eventually generates an extremely reactive carbocation as the key intermediate. The detailed reaction profile could be elucidated through multifaceted electrochemical studies and the examination of the reaction kinetics. Ultimately, a new dimension in the activation strategies for organoboron compounds was accomplished through the electrochemically driven reaction development.

Synthesis of Borylated Hydrazino Acid Derivatives

Abstractα-Boryl-α-hydrazinoacetic acid is a highly functionalized boron-containing building block that can be easily accessed from readily available α-borylacetaldehyde. The hydrazine motif can be converted into a variety of α-borylated azoles and diazines in a straightforward protocol. Furthermore, the carboxy group can be derivatized to afford novel organoboron compounds that should find applications in various cross-coupling transformations.