Remarkably Facile Borane-Promoted, Rhodium-Catalyzed Asymmetric Hydrogenation of Tri- and Tetrasubstituted Alkenes

Shoba, Veronika M.; Takacs, James M.

doi:10.1021/jacs.7b02581

Cited by 32 publications

(9 citation statements)

References 55 publications

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“…The use of 0.5 equiv of HBpin could perfectly promote the hydrogenation reaction (eq 4). These results indicated that the HBpin or boronic group might promote the trisubstituted alkenylboronate hydrogenation process . These control reactions suggested that the reaction should undergo alkyne hydroboration followed by the HBpin-promoted alkene hydrogenation pathway.…”

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confidence: 99%

Cobalt-Catalyzed Asymmetric Sequential Hydroboration/Hydrogenation of Internal Alkynes

et al. 2017

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A highly regio- and enantioselective cobalt-catalyzed hydroboration/hydrogenation of internal alkynes with HBpin and a hydrogen balloon in one pot was developed. A new type of chiral imidazoline iminopyridine (IIP) ligand was introduced for the first time in this novel and efficient strategy. This protocol used relatively simple and available starting materials with good functional group tolerance to construct more valuable chiral secondary organoboronates. The primary mechanistic studies illustrated that the cobalt-catalyzed regioselective hydroboration of alkynes did initially occur followed by HBpin-promoted and cobalt-catalyzed enantioselective hydrogenation of alkenylboronates.

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confidence: 99%

Cobalt-Catalyzed Asymmetric Sequential Hydroboration/Hydrogenation of Internal Alkynes

et al. 2017

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“…In contrast, the 3‐ and 2‐thienyl derivatives are efficient substrates in the T2 b ‐catalyzed reaction, affording 5 o (85 %, 98:2 er) and 5 p (71 %, 96:4 er), respectively. The benzofuran derivative 3 q provides good regio‐ and enantioselectivity for 5 q (40 %, 94:6 er); the moderate yield reflects competing reduction in this case . The yields, regioselectivity, and enantioselectivity obtained for 5 k (60 %, 94:6) and 5 l (65 %, 95:5) are similar to those observed for the corresponding γ‐borated products.…”

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confidence: 99%

Ligand‐Controlled Regiodivergent Enantioselective Rhodium‐Catalyzed Alkene Hydroboration

2019

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Regiocontrol in the rhodium‐catalyzed boration of vinyl arenes is typically dominated by the presence of the conjugated aryl substituent. However, small differences in TADDOL‐derived chiral monophosphite ligands can override this effect and direct rhodium‐catalyzed hydroboration of β‐aryl and β‐heteroaryl methylidenes by pinacolborane to selectively produce either chiral primary or tertiary borated products. The regiodivergent behavior is coupled with enantiodivergent addition of the borane. The nature of the TADDOL backbone substituents and that of the phosphite moiety function synergistically to direct the sense and extent of regioselectivity and enantioinduction. Twenty substrates are shown to undergo each reaction mode with regioselectivity values reaching greater than 20:1 and enantiomer ratios reaching up to 98:2. A variety of subsequent transformations illustrate the potential utility of each product.

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“…An intriguing mode of olefin activation was recently disclosed by Takacs and co-workers at the University of Nebraska− Lincoln. 56 The group reported a remarkably facile boranepromoted, oxime-directed, and Rh-catalyzed AHTOs in high yields and with high selectivities (Figure 23). The mild protocol required short reaction times and only a slight excess above stoichiometric H 2 .…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

Recent Advances in Asymmetric Hydrogenation of Tetrasubstituted Olefins

2017

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The asymmetric hydrogenation of tetrasubstituted olefins provides direct access to very useful biological molecules and intermediates. The development of the technology has been slow, due in part to the synthetic challenges involved in developing chiral catalysts for a successful asymmetric induction. We briefly recount the breakthroughs in functionalized and unfunctionalized tetrasubstituted olefins, from the reports of Zhou and Buchwald for functionalized and unfunctionalized substrates, respectively, to the advent of chiral phosphoramidite ligands. The main emphasis of this Perspective lies in bringing into focus the complexity and challenges of inducing an asymmetric reduction for these substrates, which includes a brief discussion of the mechanism, the latest developed chiral catalysts, and the enormous scientific opportunities that still exist in developing "go to" catalyst systems for the various substrate types.

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Remarkably Facile Borane-Promoted, Rhodium-Catalyzed Asymmetric Hydrogenation of Tri- and Tetrasubstituted Alkenes

Cited by 32 publications

References 55 publications

Cobalt-Catalyzed Asymmetric Sequential Hydroboration/Hydrogenation of Internal Alkynes

Cobalt-Catalyzed Asymmetric Sequential Hydroboration/Hydrogenation of Internal Alkynes

Ligand‐Controlled Regiodivergent Enantioselective Rhodium‐Catalyzed Alkene Hydroboration

Recent Advances in Asymmetric Hydrogenation of Tetrasubstituted Olefins

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