Carbodiphosphorane-Catalyzed Hydroboration of Ketones and Imines

Abstract

We report the use of a cyclic carbodiphosphorane catalyst for ketone and imine hydroboration reactions. To our knowledge, this represents the first use of a carbodiphosphorane as an organocatalyst. The carbodiphospohorane shows superior catalytic activity compared to other neutral carbon nucleophiles tested.

Cyclobutenylidene: A Multifaceted Two-Coordinate Carbon Species Obtained via Skeletal Editing of a Cyclopropenylidene

“…The reaction of acetophenone and pinacole borane (HBPin) in the presence of 5 mol % of 1 at r.t. yielded the hydroborated product 10 in 63% yield after 1 h, 95% yield after 24 h, and 98% yield after 3 days which brings into light the utility of CBYs as organocatalysts (Figures S63–S66). This reaction is faster than the same reaction catalyzed by IPr (IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene) or N-heterocyclic olefin IPrCH 2 (IPr: 17%, IPrCH 2 33% after 24 h) but slower than that catalyzed by a cyclic carbodiphosphorane (99% after 1 h) under a similar reaction condition (5 mol % catalyst loading, C 6 D 6 , 25 °C). , …”

“…This reaction is faster than the same reaction catalyzed by IPr (IPr = 1,3-bis(2,6diisopropylphenyl)imidazol-2-ylidene) or N-heterocyclic olefin IPrCH 2 (IPr: 17%, IPrCH 2 33% after 24 h) but slower than that catalyzed by a cyclic carbodiphosphorane (99% after 1 h) under a similar reaction condition (5 mol % catalyst loading, C 6 D 6 , 25 °C). 59,60 The ability of SiCBY 1 to exhibit properties of an ambiphilic carbene and a carbone could be explained by the noninnocent character of the cyclobutene framework deriving from the exocyclic amino groups (Figure 4b). In the coordination sphere of Lewis acids (e.g., complexes 2 and 3), the SiCBY moieties show only a small deviation from the free SiCBY (C1−C2 bond: 4)°) is a typical structural feature for a cyclobutene but completely different from the structural features of the SiCBY moieties within 2, 3, and 9.…”

Applications of catalysis in hydroboration of imines, nitriles, and carbodiimides

“…53 Following such pioneering works, other metal and non-metal main group complexes were developed in related hydroboration transformations. [53][54][55][56][57][58][59][60][61][62][63][64][65] Catalyst free imine hydroboration was also recently introduced by the Rit group. 66 Nitrile hydroboration, operating through the formation of an imine intermediate, 49 was only introduced less than a decade ago by Nikonov and co-workers who employed an imido-hydrido complex of Mo(IV).…”

“…53 Following such pioneering works, other metal and non-metal main group complexes were developed in related hydroboration transformations. 53–65 Catalyst free imine hydroboration was also recently introduced by the Rit group. 66…”

Theoretical Photoelectron Spectroscopy of Low-Valent Carbon Species: A ∼6 eV Range of Ionization Potentials among Carbenes, Ylides, and Carbodiphosphoranes

“…Although the first CDP was reported over half a century ago, the CDP field has recently undergone a renaissance . Thus, CDPs have been recognized as superbases, , as superbase catalysts, and as potentially doubly dative ligands toward main-group, − d-block, and f-block , complexes. Recently, a second class of zero-valent carbon compounds (also called carbones) has emergedthe carbodicarbenes (CDCs) − in which nucleophilic carbenes take the place of phosphines in CDPs.…”