Rhodium catalysed dehydrogenative borylation of alkenes: Vinylboronates via C–H activation

Mkhalid, I.A.; Coapes, R. Benjamin; Edes, S. Natasha; Coventry, David N.; Souza, Fabio E. S.; Thomas, Rhodri Ll.; Hall, Jonathan; Bi, Siwei; Lin, Zhenyang; Marder, Todd B.

doi:10.1039/b715584k

Cited by 116 publications

(67 citation statements)

References 81 publications

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“…50,52,66−69 To address this question, we examined pathway II , which differs from the family of mechanisms described under pathway I in that pathway II involves the migratory insertion of the coordinated alkene into the Rh–B bond. 70−72 To accommodate the desired migratory insertion, pinBH adds to Im0 in a direction more perpendicular (rather than parallel, as previously examined) to the coordination plane encompassing Rh (Figure 7).…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Insights into Carbonyl-Directed Rhodium-Catalyzed Hydroboration: ab Initio Study of a Cyclic γ,δ-Unsaturated Amide

et al. 2014

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A two-point binding mechanism for the cationic rhodium(I)-catalyzed carbonyl-directed catalytic asymmetric hydroboration of a cyclic γ,δ-unsaturated amide is investigated using density functional theory. Geometry optimizations and harmonic frequency calculations for the model reaction are carried out using the basis set 6-31+G** for C, O, P, B, N, and H and LANL2DZ for Rh atoms. The Gibbs free energy of each species in THF solvent is obtained based on the single-point energy computed using the PCM model at the ECP28MWB/6-311+G(d,p) level plus the thermal correction to Gibbs free energy by deducting translational entropy contribution. The Rh-catalyzed reaction cycle involves the following sequence of events: (1) chelation of the cyclic γ,δ-unsaturated amide via alkene and carbonyl complexation in a model active catalytic species, [Rh(L2)2S2]+, (2) oxidative addition of pinacol borane (pinBH), (3) migratory insertion of the alkene double bond into Rh–H (preferred pathway) or Rh–B bond, (4) isomerization of the resulting intermediate, and finally, (5) reductive elimination to form the B–C or H–C bond with regeneration of the catalyst. Free energy profiles for potential pathways leading to the major γ-borylated product are computed and discussed in detail. The potential pathways considered include (1) pathways proceeding via migratory insertion into the Rh–H bond (pathways I, I-1, and I-2), (2) a potential pathway proceeding via migratory insertion into the Rh–B bond (pathway II), and two potential competing routes to a β-borylated byproduct (pathway III). The results find that the Rh–H migratory insertion pathway I-2, followed in sequence by an unanticipated isomerization via amide rotation and reductive elimination, is the most favorable reaction pathway. A secondary consequence of amide rotation is access to a competing β-hydride elimination pathway. The pathways computed in this study are supported by and help explain related experimental results.

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Section: Resultsmentioning

confidence: 99%

Mechanistic Insights into Carbonyl-Directed Rhodium-Catalyzed Hydroboration: ab Initio Study of a Cyclic γ,δ-Unsaturated Amide

et al. 2014

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“…14 A more selective palladium-catalyzed method has since been described but is restricted to terminal alkenes bearing electronically activating groups such as aryl and alkenyl substituents (Scheme 2A). 15 …”

Section: Introductionmentioning

confidence: 99%

Cobalt-Catalyzed 1,1-Diboration of Terminal Alkynes: Scope, Mechanism, and Synthetic Applications

2017

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A cobalt-catalyzed method for the 1,1-diboration of terminal alkynes with bis(pinacolato)diboron (B2Pin2) is described. The reaction proceeds efficiently at 23 °C with excellent 1,1-selectivity and broad functional group tolerance. With the unsymmetrical diboron reagent PinB–BDan (Dan = naphthalene-1,8-diaminato), stereoselective 1,1-diboration provided products with two boron substituents that exhibit differential reactivity. One example prepared by diboration of 1-octyne was crystallized, and its stereochemistry established by X-ray crystallography. The utility and versatility of the 1,1-diborylalkene products was demonstrated in a number of synthetic applications, including a concise synthesis of the epilepsy medication tiagabine. In addition, a synthesis of 1,1,1-triborylalkanes was accomplished through cobalt-catalyzed hydroboration of 1,1-diborylalkenes with HBPin. Deuterium-labeling and stoichiometric experiments support a mechanism involving selective insertion of an alkynylboronate to a Co–B bond of a cobalt boryl complex to form a vinylcobalt intermediate. The latter was isolated and characterized by NMR spectroscopy and X-ray crystallography. A competition experiment established that the reaction involves formation of free alkynylboronate and the two boryl substituents are not necessarily derived from the same diboron source.

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“…[1] Avariety of transition-metal complexes such as rhodium(I), [2] iridium(I), [3] ruthenium(II), [4] iron(0), [5] and cobalt(I) [6] catalyze the hydroboration of terminal alkenes with pinacolborane (HBpin), thus forming alkyl pinacolboronates in ar egioselective way [ Figure 1a]. [10,11] Herein, we report ar hodium(I)-catalyzed reaction of aliphatic terminal alkenes with HBpin, which preferentially produce dehydrogenative borylation compounds (Figure 1b). [7][8][9] For example,M asuda et al reported that the reaction of styrene with HBpin in the presence of neutral [RhCl(cod)] 2 gave the dehydrogenative borylation product along with as mall amount of the hydroboration products.…”

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confidence: 99%

Rhodium‐Catalyzed Dehydrogenative Borylation of Aliphatic Terminal Alkenes with Pinacolborane

2015

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Aliphatic terminal alkenes react with pinacolborane at ambient temperature to affordd ehydrogenative borylation compounds as the major product when iPr-Foxap is used as the ligand with cationic rhodium(I) in the presence of norbornene, which acts as the sacrificial hydrogen acceptor.The reaction is applied to the one-pot syntheses of aldehydes and homoallylic alcohols from aliphatic terminal alkenes.

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Rhodium catalysed dehydrogenative borylation of alkenes: Vinylboronates via C–H activation

Cited by 116 publications

References 81 publications

Mechanistic Insights into Carbonyl-Directed Rhodium-Catalyzed Hydroboration: ab Initio Study of a Cyclic γ,δ-Unsaturated Amide

Mechanistic Insights into Carbonyl-Directed Rhodium-Catalyzed Hydroboration: ab Initio Study of a Cyclic γ,δ-Unsaturated Amide

Cobalt-Catalyzed 1,1-Diboration of Terminal Alkynes: Scope, Mechanism, and Synthetic Applications

Rhodium‐Catalyzed Dehydrogenative Borylation of Aliphatic Terminal Alkenes with Pinacolborane

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