Marc Devillard

We report a straightforward and catalyst-free synthetic methodology for accessing α-aminoboron compounds incorporating the N–CH ₂ –B motif through the double hydroboration of various isocyanides using diisopropylaminoborane (DIAB).

The reactivity of well-defined silyl-substituted alkenylalanes has been studied in the presence of anions, Lewis bases and benzophenone. In the presence of methyllithium or fluoride anions, the corresponding methyl- or fluoro-aluminates bearing alkenyl substituents of Z configuration have been fully characterized including by X-ray diffraction analysis. The configurational stability of these ate complexes toward Z-to-E isomerization revealed substituent-dependent and was examined on the basis of experiments and DFT calculations. In a second step, the fate of benzonitrile and ketone adducts of the alkenylalanes was investigated. Whereas the benzonitrile adducts revealed thermally stable, the corresponding Ph₂C═O → Al(alkenyl)₃ adducts evolved to the alkoxyaluminums due to the transfer of a α-hydride from an alkenyl substituent to the activated carbonyl function. The mechanism of this uncommon reduction could be unveiled and compared to more classical alkyl- and alkenyl-groups migration processes.

A methodology to access Z-1-silyl-2-aluminyl-disubstituted olefins is developed. It relies on the uncatalyzed ring opening of silacyclopropenes in the presence of a stoichiometric amount of trimethylaluminum. The resulting heterosubstituted alkenes exhibit a particular interaction between the electron-rich [Si-CH3] moiety and the electron-deficient diorganoaluminyl group, resulting in similar geometrical features due to the proximity of these two centers. This interaction is rationalized using experimental and theoretical descriptors. The regioselectivity and functional tolerance of the methylalumination were also studied in the case of unsymmetrical silacyclopropenes, and the methodology ultimately transposed to the synthesis of a polymeric organoalane incorporating tricoordinated aluminum centers.

The synthetic methodology for the preparation of photoresponsive dioxazaborocanes‐containing oligomers is developed. It relies on the transformation of the (diisopropylamino)boryl group (−BH(NiPr₂)) into a dioxazaborocane unit in the presence of β‐aminodiols and involves a bis‐borylated dithienylethene photochromic unit. The photophysical properties of the obtained oligomers are evaluated as well as their processability for the preparation of spin‐coated films. The photomechanical behavior of the resulting films is assessed via displacement tracking profile.

The synthesis of phosphines with light controlled basicity is presented in this study. A methodological approach for the preparation of these unconventional photochromic phosphines based on a dithienylethene organic moiety is reported. It relies on the palladium‐catalyzed annulation of alkynyl phosphines in the presence of a 2,3‐Dithienylsilacyclopropene. Accordingly, a diphenyphosphino moiety is connected to the organic photochrome thanks to different linkers. Their influence on the photochromism and on the phosphinyl group basicity is studied and evaluated based on experimental an NMR descriptor as well as DFT calculations.

The palladium-catalyzed annulation reaction of alkynes enables an attractive approach to siloles. Their access from silirenes and terminal alkynes proved rather general, involving reactive intermediates that have remained elusive to date. Starting from 1,2-bis(3-thienyl)silirene as a source of photochromic siloles, the mechanism of the annulation reaction has been revisited, and palladasilacyclobutenes resulting from the activation of the silirene could be isolated and thoroughly characterized (NMR, X-ray, and DFT). Their role as reactive intermediates and their fate in the course of the reaction were also studied in situ. In combination with in-depth DFT calculations, a clearer picture of the mechanism and the reactive key species is disclosed.

The direct access to (mesityl)(alkyl)haloboranes (Mes(Alk)BX) (X = Br, Cl) from mesitylborane dimer and vinyl halides is presented, revealing two accessible pathways, one of which being kinetically favoured.

Multiply bonded boron species are fascinating objects of study addressing concerns about the chemical bonding. Although mostly exemplified with light p‐block elements, the use of Group 6–10 transition metals as models to more clearly understand and rationalize the bonding in this family of compounds has also proved successful. In this prospect, the interplay between experiment and theory pushes forward the frontiers of the analysis based on the metric parameters, and it clearly appears that the notion of doubly or triply bonded boron in such species must be qualified. The bond orders are more often partial involving more or less polarized bonds responsible for the chemical reactivity. These features are developed in this chapter starting with the nearest neighbors of boron and finishing with the case of transition metals.