The quantification of Lewis acidity is accomplished by a deuterated quinolizidine probe utilizing 2H NMR spectroscopy. The chemical shifts of the 2H NMR signals for aluminum, boron, titanium, and zinc halides are reported. The rate constants for Lewis acid catalyzed reactions were determined by utilizing UV/Vis spectroscopy for Diels–Alder and Povarov reactions under pseudo‐first‐order conditions. The magnitude of the 2H NMR chemical shifts correlates with the rate constants of the organic transformations for many Lewis acids investigated in the same order, whereas some deviations are identified.

Terminal and internal alkynes are efficiently hydroborated to (E)-alkenyl pinacol boronic esters with excellent yields and selectivities using a Lewis acid catalyst. In the case of Piers' borane (HB(C6F5)2) the borane acts as a pre-catalyst generating dissymmetrically gem-diborylated species of the form RCH2CR'(Bpin)(B(C6F5)2) which are the active catalysts.

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Two (aryl)PXY starting materials (aryl = mesityl or 2,4,6-triisopropylphenyl; X,Y = Cl, Br) were reacted with lithiated conjugated enynes (derived from 2-methylbutenyne or 1-ethynylcyclohexene) to yield the respective (aryl)bis(enynyl)phosphanes. Their reaction with HB(C6F5)2 gave the heterocyclic five-membered zwitterionic borata-diene compounds containing the aryl group and one unchanged enynyl substituent at phosphorus. The borata-alkene products were thought to arise from a two step process of regioselective alkyne hydroboration followed by an internal phosphane attack on the boryldiene unit. Three examples of the ring-closed borata-alkene type products were characterized by X-ray diffraction.