Cyclische Allene und Cumulene durch kooperative Addition frustrierter Lewis‐Paare an konjugierte Enine und Diine

A Highly Reactive Geminal P/B Frustrated Lewis Pair: Expanding the Scope to C−X (X=Cl, Br) Bond Activation

“…[22] An almost-planar,f ive-membered, air-and moisture-stable heterocycle with an exocyclic C=O double bond is formed (6). The corresponding 13 CNMR signal appearsa t1 68.3 ppm, in good agreement with the shift reported for the literature-knowns ystem mentioned above (167.8 ppm). An analogouss tructure to 6 is obtained from 1 and CS 2 (7).…”

“…[33] In the case of 9,w ef ound ap roton resonance at 1.88 ppm (d, 3 J(H,P) = 4.9 Hz) with an integral of 3H,a ssignablet oaCH 3 group. The corresponding 13 CNMR signal was observeda t2 6.5 ppm (d, 2 J(C,P) = 47 Hz). The mo-lecular structure of 9 in the solid state shows an endocyclic CÀ Nd istance of 1.258 (10) and an exocyclic CÀCd istance of 1.505(10),w hich are typical values of C=Nb onds [38] and C(sp 2 )ÀC(sp 3 )s ingle bonds, [39] respectively.W et herefore conclude that 9 is the imine rather than the enamine tautomer.I n contrastt ot he adduct of Nçth et al, 9 is thermally stable up to 120 8C.…”

“…For example, Erker and co-workerss tudied as eries of compounds R 2 P(CH 2 ) n B(C 6 F 5 ) 2 (n = 2-4) and found the ethylene-and butylene-bridged species to be active FLPs (e.g.,f or H 2 cleavage), whereas the propylene derivative showedn oi ndication of typical FLP activity. [8][9][10][11][12][13][14] Methylene-bridged P/B pairs differ fundamentally from the abovementioned C 2 -, C 3 -, and C 4 -linked compounds, because ao ne-atoms pacerl eads to less conformational flexibility of the molecular scaffold and thus to aw ell-defined P···Bd istance.M oreover,t he degree of intramolecular P/B interaction shouldb es mall, because formation of aP ÀB s bond would result in as trained three-membered ring and, in contrastt o phosphinoboranes (C 0 species), [15,16] P=B p donation is not possible. Thus, in ag eminal P/B FLP,t he two reactive sites should be perfectly preoriented for small-molecule activation.…”

Reaction of Frustrated Lewis Pairs with Conjugated Ynones‐Selective Hydrogenation of the Carbon–Carbon Triple Bond

“…[1] They add to alkenes and alkynes, [2] add to various carbonyl compounds, including carbon dioxide, [3] and undergo unique 1,4-addition reactions to conjugated enynes and diynes to yield zwitterionic cumulene derivatives. [4] Most notably many FLPs split dihydrogen heterolytically, some reversibly, and are able to transfer the resulting P/B or N/B bonded H + /H À pair to selected unsaturated substrates. [5] This ability has resulted in the development of a small series of metal-free catalytic hydrogenation processes; some frustrated Lewis pairs are able to serve as hydrogenation catalysts for bulky imines, enamines, or silylenolethers.…”

Reaktionen frustrierter Lewis‐Paare mit konjugierten Inonen – selektive Hydrierung der Kohlenstoff‐Kohlenstoff‐Dreifachbindung

“…

Professor Siegfried Hünig zum 90. [4] Bemerkenswert ist die Fähigkeit vieler FLPs, Diwasserstoff heterolytisch zu spalten und das resultierende P/Boder N/B-gebundene H + /H À -Paar auf bestimmte ungesättigte Substrate zu übertragen. [1] Sie addieren an Alkene und Alkine, [2] an verschiedene Carbonylverbindungen, einschließlich Kohlendioxid, [3] und sie gehen ungewöhnliche 1,4-Additionen mit konjugierten Eninen und Diinen unter Bildung zwitterionischer Cumulenderivate ein.

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