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.

Bending the planar trigonal boron center of triphenylborane by connecting its aryl rings with carbon or phosphorus linkers gave access to a series of 9‐boratriptycene derivatives with unprecedented structures and reactivities. NMR spectroscopy and X‐ray diffraction 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 a trivalent boron compounds with the Tf2N− anion illustrates the unrivaled Lewis acidity of these species. Increasing the pyramidalization of the boron center and using a cationic phosphonium linker resulted in an exceptional enhancement of Lewis acidity. Introduction of a phosphorus and a boron atom at each edge of a triptycene framework, allowed access to new bifunctional Lewis acid‐base 9‐phospha‐10‐boratriptycenes featuring promising reactivity for the activation of carbon‐halogen bonds.

Although boron Lewis acids commonly adopt a trigonal planar geometry, a number of compounds in which the trivalent boron atom is located in a pyramidal environment have been described. This review will highlight the recent developments of the chemistry and applications of non-planar boron Lewis acids, including a series of non-planar triarylboranes derived from the triptycene core. A thorough analysis of the properties and of the influence of the pyramidalization of boron Lewis acids on their stereoelectronic properties and reactivities is presented based on recent theoretical and experimental studies.1 Non-planar Trialkylboranes2 Non-planar Alkyl and Aryl-Boronates3 Non-planar Triarylboranes and Alkenylboranes3.1 Previous Investigations on Bora Barrelenes and Triptycenes3.2 Recent Work on Boratriptycenes from Our Research Group4 Applications of Non-planar Boranes4.1 Non-planar Alkyl Boranes and Boronates4.2 Non-planar Triarylboranes (Boratriptycenes)5 Other Non-planar Group 13 Lewis Acids6 Further Work and Perspectives

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