Catalytic metal-free Si–N cross-dehydrocoupling

Greb, Lutz; Tamke, Sergej; Paradies, Jan

doi:10.1039/c3cc49558b

Cited by 116 publications

(79 citation statements)

References 48 publications

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“…Overall, this catalytic cycle is computed to be slightly exothermic (ΔH = −6.0 kcal·mol −1 ) with only a small overall ΔG of −0.6 kcal·mol −1 . This dehydrocoupling mechanism is reminiscent of that described for analogous B(C 6 F 5 ) 3 catalyzed reaction in the classic work from Piers and coworkers (29), which subsequently further illuminated and expanded by the groups of Oestreich (30), Brook (31), Rubinsztajn (32), and Paradies (33). In the context of dehydrocoupling, it is also important to note the pioneering work from the Tilley and Manners research groups, who exploited transition metal catalysts for this purpose (34,35), whereas Hill et al (36) described Zn, Mg, Ca, and Sr catalyzed preparations of amino silanes and Baba and coworker (37) have used InBr 3 to dehydrocouple silanes and carboxylic acids (Table 1 and Fig.…”

Section: Resultsmentioning

confidence: 92%

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

Pérez

Caputo

Dobrovetsky

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

145

111

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A major advance in main-group chemistry in recent years has been the emergence of the reactivity of main-group species that mimics that of transition metal complexes. In this report, the Lewis acidic phosphonium salt [(C 6 F 5 ) 3 PF][B(C 6 F 5 ) 4 ] 1 is shown to catalyze the dehydrocoupling of silanes with amines, thiols, phenols, and carboxylic acids to form the Si-E bond (E = N, S, O) with the liberation of H 2 (21 examples). This catalysis, when performed in the presence of a series of olefins, yields the concurrent formation of the products of dehydrocoupling and transfer hydrogenation of the olefin (30 examples). This reactivity provides a strategy for metalfree catalysis of olefin hydrogenations. The mechanisms for both catalytic reactions are proposed and supported by experiment and density functional theory calculations. fluorophosphonium A wide range of commodity chemicals, petrochemicals, pharmaceuticals, materials, and foods depend on industrial-scale hydrogenation reactions. Catalysts for this process are based on both heterogeneous transition metals materials and homogeneous transition metal complexes. Indeed, it was the discovery of Sabatier (1) in the early 20th century that revealed the utility of amorphous Ni and other metals in hydrogenation processes. Following the dawn of organometallic chemistry in the 1960s, homogeneous catalysts were developed principally based on precious metals (2-4). Although subsequent modifications and optimizations have led to numerous highly selective and efficient catalyst technologies, concerns over cost, natural abundance, and toxicity have prompted efforts to uncover catalysts based on "earth-abundant" elements. The principal targets in these efforts have been the first-row transition metals. Indeed, the groups of Chirik (5, 6), Morris (7), Beller (8), and others (9) have developed remarkably active and selective catalysts based on Fe.Strategies to develop reduction methods using organic or main-group-based reagents have also been explored. For example, use of Hantzsch esters (10), Birch reduction of arenes (11), or the use of B or Al hydrides are effective, albeit stoichiometric reductions. More recently, the advent of "frustrated Lewis pairs" (FLPs) have led to the discovery that combinations of sterically encumbered donors and acceptors act as catalysts for the reductions of imines, enamines, silylenol ethers, olefins, and alkynes (12).To uncover hydrogenation strategies using earth-abundant elements, we have focused our efforts on Lewis acidic phosphorus species. Although Gudat (13), Burford and coworker (14), Yoshifuji (15), and Bertrand and coworker (16), among others, have reported phosphenium cations that demonstrate Lewis acidity, Radosevich and coworkers (17) have exploited the reaction of the unique planar P(III) species with ammoniaborane to give a P(V)H 2 derivative that effects the subsequent reduction of diazobenzene. Although the acidity of P(V) has been exploited previously in ylide reagents (18), Diels-Alder reactions catalysis (19), and add...

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Section: Resultsmentioning

confidence: 92%

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

Pérez

Caputo

Dobrovetsky

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

145

111

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“…Paradies and co-workers [46] have recently reported the dehydrocoupling of a variety of secondary amines and silanes catalyzed by B(C 6 F 5 ) 3 . These reactions are thought to proceed by reactive intermediate silylammonium/hydridoborate ion pairs (e.g.…”

Section: Hydrogen Splitting and Metal-free Hydrogenationmentioning

confidence: 98%

Frustrated Lewis Pair Chemistry: Development and Perspectives

2015

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Frustrated Lewis pairs (FLPs) are combinations of Lewis acids and Lewis bases in solution that are deterred from strong adduct formation by steric and/or electronic factors. This opens pathways to novel cooperative reactions with added substrates. Small-molecule binding and activation by FLPs has led to the discovery of a variety of new reactions through unprecedented pathways. Hydrogen activation and subsequent manipulation in metal-free catalytic hydrogenations is a frequently observed feature of many FLPs. The current state of this young but rapidly expanding field is outlined in this Review and the future directions for its broadening sphere of impact are considered.

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“…44 2.3.3 Si-N bond formation. 46 Here too the potential for the N lone pair to coordinate to the Lewis acid catalyst can potentially prove problematic for less sterically hindered primary amines (cf. 45 However alternative methods such as dehydrocoupling which do not release HCl are of interest.…”

Section: Si-s Bond Formationmentioning

confidence: 99%

“…Si-N bonds are usually synthesised by the aminolysis of chlorosilanes. 46 Carbazoles have also been used as substrates giving the Si-N products in 83-97% yields using 1 mol% catalyst. The dehydrogenic Si-N coupling between hydrosilanes and anilines, carbazoles and indoles have all been catalysed using B(C 6 F 5 ) 3 (Scheme 21, also see ESI, † Table S4).…”

Section: Si-s Bond Formationmentioning

confidence: 99%

“…45 However alternative methods such as dehydrocoupling which do not release HCl are of interest. 46 The dehydrocoupling of diamine, pyrrole and indole derivatives were also examined. 46 Here too the potential for the N lone pair to coordinate to the Lewis acid catalyst can potentially prove problematic for less sterically hindered primary amines (cf.…”

Section: Si-s Bond Formationmentioning

confidence: 99%

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Dehydrocoupling routes to element–element bonds catalysed by main group compounds

Melen

2016

Chem. Soc. Rev.

118

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Dehydrocoupling reactions, i.e. reactions involving elimination of H2 between two E-H bonds, provide a clean route to E-E bonds within the main group. The products afforded from these reactions have applications in organic synthesis and materials chemistry, and in addition the H2 released during these reactions can also be useful as an energy source. Previous methods for dehydrocoupling involve both thermal and transition metal catalysed routes but recent developments have shown that main group compounds can be used as catalysts in these reactions. This tutorial review will focus on the development of main group catalysed dehydrocoupling reactions as a route to heteronuclear element-element bonds.

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Catalytic metal-free Si–N cross-dehydrocoupling

Cited by 116 publications

References 48 publications

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

Frustrated Lewis Pair Chemistry: Development and Perspectives

Dehydrocoupling routes to element–element bonds catalysed by main group compounds

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