Grignard Reagent-Catalyzed Hydroboration of Esters, Nitriles, and Imines.

The reduction in esters, nitriles, and imines requires harsh conditions (highly reactive reagents, high temperatures, and pressures) or complex metal-ligand catalytic systems. Catalysts comprising earth-abundant and less toxic elements are desirable from the perspective of green chemistry. In this study, we developed a green hydroboration protocol for the reduction in esters, nitriles, and imines at room temperature (25 °C) using pinacolborane as the reducing agent and a commercially available Grignard reagent as the catalyst.

DIBALH: from known fundamental to an unusual reaction; chemoselective partial reduction of tertiary amides in the presence of esters.

This study presents a quick and reliable approach to the chemoselective partial reduction of tertiary amides to aldehydes in the presence of readily reducible ester groups using commercial DIBALH reagent. Moreover, the developed method was also extended to multi-functional molecules bearing ester moieties, which were successfully chemoselectively reduced to the corresponding aldehydes.

Lithium bromide: an inexpensive and efficient catalyst for imine hydroboration with pinacolborane at room temperature.

An efficient protocol for the hydroboration of imines is reported. Lithium halide salts are effective catalysts to convert aldimines and ketimines to their corresponding amines. Here, we report excellent isolated yield of secondary amines (>95%) using 3 mol% lithium bromide in THF at room temperature.

Deboronation-Induced Ratiometric Emission Variations of Terphenyl-Based --Carboranyl Compounds: Applications to Fluoride-Sensing.

--carboranyl compounds bearing the -type perfectly distorted or planar terphenyl rings (- and -, respectively) and their -derivatives (- and -, respectively) were synthesized and fully characterized using multinuclear NMR spectroscopy and elemental analysis. Although the emission spectra of both -compounds exhibited intriguing emission patterns in solution at 298 and 77 K, in the film state, - mainly exhibited a π-π* local excitation (LE)-based emission in the high-energy region, whereas - produced an intense emission in the low-energy region corresponding to an intramolecular charge transfer (ICT) transition. In particular, the positive solvatochromic effect of - and theoretical calculation results at the first excited (S) optimized structure of both -compounds strongly suggest that these dual-emissive bands at the high- and low-energy can be assigned to each π-π* LE and ICT transition.

Planarity of terphenyl rings possessing o-carborane cages: turning on intramolecular-charge-transfer-based emission.

To clarify the relationship between planarity and intramolecular charge transfer (ICT), two o-carboranyl compounds (TCB and FCB) containing different ortho-type terphenyl rings, namely, perfectly distorted or planar phenyl rings, were synthesised and fully characterised. Although the emission spectra of both compounds presented intriguing dual-emission patterns in solution at 298 or 77 K and in the film state, distorted TCB mostly showed locally excited emission, whereas planar FCB demonstrated intense emission corresponding to an ICT transition. Interestingly, the emission efficiencies and radiative decay constants of terphenyl-based o-carboranyl compounds were gradually enhanced by increasing the planarity of the terphenyl groups.

Catalytic Hydroboration of Aldehydes, Ketones, and Alkenes Using Potassium Carbonate: A Small Key to Big Transformation.

An efficient transition-metal-free protocol for the hydroboration of aldehydes and ketones (reduction) was developed. The hydroboration of a wide range of aldehydes and ketones with pinacolborane (HBpin) under the KCO catalyst has been studied. The reaction system is practical and reliable and proceeds under extremely mild and operationally simple conditions.

Alkene hydroboration with pinacolborane catalysed by lithium diisobutyl--butoxyaluminum hydride.

Here we developed a highly efficient alkene hydroboration protocol, showing that various alkyl boronates can be smoothly obtained in good yields by reacting alkenes with pinacolborane (HBpin) in the presence of 5 mol% lithium diisobutyl--butoxyaluminum hydride. The coordination of aluminate ions with lithium cations allowed for effective hydride transfer during hydroboration, and the obtained boronate ester was further used for C-C coupling, trifluoroboronate salt formation, and oxidation to alcohol.

A new and general one-pot synthesis of propargyl alcohols from esters.

Intermediates easily prepared by partial reduction of various esters with LDBBA as a reducing agent smoothly react with lithium acetylides to give propargyl alcohols, without isolation of partial reduction intermediates, in good yields (73-83%).