Endohedral Functionalized Cage as a Tool to Create Frustrated Lewis Pairs

Abstract

Afrustrated Lewis pair (FLP) system was obtained by confinement of the Lewis base partner,aVerkadess uperbase,i nam olecular cavity.W hereas the model superbase lacking cavity displayed no catalytic activity in Morita-Baylis-Hillman (MBH) reactions,w hen associated to titanium (IV) chloride,t he encaged superbase turns out to be an efficient catalyst under the same conditions.T he crucial role of the endohedral functionalized cage on catalytic performance was further demonstrated by the fact that model superbases with bulky substituents were muchl ess efficient to produce active catalysts,a sw ell as by inhibition and substrate selection experiments. 31 PNMR spectroscopya nd mass spectrometry experiments evidenced that no interaction between the Lewis acidic and basic partners occurred when the superbase was capped by ac ycloveratrylene (CTV) unit, thus creating at rue FLP active system.

Engineering an efficient and enantioselective enzyme for the Morita–Baylis–Hillman reaction

“…Spectral data is consistent with literature values. 46 1 H NMR (400 MHz, CDCl 3 ) δ 7.24 (d, J = 8.1 Hz, 2H), 7.15 (d, J = 7.9 Hz, 2H), 6.74 (t, J = 4.2 Hz, 1H), 5.52 (s, 1H), 3.36 (br s, 1H), 2.48 – 2.42 (m, 2H), 2.42 – 2.35 (m, 2H), 2.34 (s, 3H), 2.04 – 1.95 (m, 2H). 13 C NMR (126 MHz, CDCl 3 ) δ 200.6, 147.4, 141.3, 138.8, 137.3, 129.2, 126.5, 72.6, 38.8, 25.9, 22.7, 21.3.…”

Reactions in Endohedral Functionalized Cages

“…This report is the first example of an encaged superbase as organocatalyst. In a later study, 24 has been shown to form a frustrated Lewis‐pair (FLP) with TiCl 4 [50] . The FLP is able to catalyze the Morita‐Baylis‐Hilman (MBH) reaction between p ‐chlorobenzaldehyde and cyclopentenone (Figure 10, right).…”

Encapsulation of Azaphosphatranes and Proazaphosphatranes in Confined Spaces

“…Then, the encaged Verkade's superbase P @ 2 a was combined with a Lewis acid, titanium (IV) chloride, in order to create a Frustrated Lewis Pair (FLP) system . It was demonstrated that the acid‐base reaction between these two partners was prevented by the confinement of the proazaphosphatrane in a cage structure.…”

“…Then, the encaged Verkade's superbase P@2 a was combined with a Lewis acid, titanium (IV) chloride, in order to create a Frustrated Lewis Pair (FLP) system. [21] It was demonstrated that the acid-base reaction between these two partners was prevented by the confinement of the proazaphosphatrane in a cage structure. Indeed, when the model P@3 a is mixed with TiCl 4 the chlorinated azaphosphatrane PCl + @3 a is formed while this process does not occur when the confined superbase is used as Lewis base (Scheme 5 (b)).…”