A highly bent triarylborane, 9‐boratriptycene, was generated in solution by selective protodeboronation of the corresponding tetra‐aryl boron ate complex with the strong Brønsted acid HNTf2. The iptycene core confers enhanced Lewis acidity to 9‐boratriptycene, making it unique in terms of structure and reactivity. We studied the stereoelectronic properties of 9‐boratriptycene by quantifying its association with small N‐ and O‐centered Lewis bases, as well as with sterically hindered phosphines. The resultant Lewis adducts exhibited unique structural, spectroscopic, and photophysical properties. Beyond the high pyramidalization of the 9‐boratriptycene scaffold and its low reorganization energy upon Lewis base coordination, quantum chemical calculations revealed that the absence of π donation from the triptycene aryl rings to the boron vacant pz orbital is one of the main reasons for its high Lewis acidity.

Bending the planar trigonal boron center of triphenylborane by connecting its aryl rings with carbon or phosphorus linkers gave access to as eries of 9-boratriptycene derivatives with unprecedented structures and reactivities. NMR spectroscopyand X-raydiffraction of the Lewis adducts of these non-planar boron Lewis acids with weak Lewis base revealed particularly strong covalent bond formation. The first Lewis adduct of at rivalent boron compounds with the Tf 2 N À anion illustrates the unrivaled Lewis acidity of these species. Increasing the pyramidalization of the boron center and using ac ationic phosphonium linker resulted in an exceptional enhancement of Lewis acidity.I ntroduction of ap hosphorus and ab oron atom at each edge of at riptycene framework, allowed access to new bifunctional Lewis acid-base 9-phospha-10-boratriptycenes featuring promising reactivity for the activation of carbon-halogen bonds.

The rational design of a geometrically constrained boron Lewis superacid featuring exceptional structure and reactivity is disclosed. It enabled the formation of non-classical electron deficient BÀHÀB type of bonding, which was supported by spectroscopic and structural parameters as well as computational studies. Taming the pyramidal Lewis acid electrophilicity through weak coordinating anion dissociation enabled a series of highly challenging chemical transformations, such as Csp 2 ÀH and Csp 3 ÀH activation under a frustrated Lewis pair regime and the cleavage of Csp 3 ÀSi bonds. The demonstration of such rich chemical behaviour and flexibility on a single molecular compound makes it a unique mediator of chemical transformations generally restricted to transition metals.

Phenylsilane was reevaluated as a useful coupling reagent for amide synthesis. At room temperature, a wide range of amides and peptides were obtained in good to excellent yields (up to 99%). For the first time, Weinreb amides synthesis mediated by a hydrosilane were also documented. Comparative experiments with various acetoxysilanes suggested the involvement of a phenyltriacyloxysilane. From this mechanistic study, silicon tetracetate was shown as an efficient amine acylating agent.