Extending the Substrate Scope in the Hydrogenation of Unfunctionalized Tetrasubstituted Olefins with Ir-P Stereogenic Aminophosphine–Oxazoline Catalysts

Biosca, Maria; Salomó, Ernest; Cruz-Sánchez, Pol de la; Riéra, Antoni; Pàmies, Òscar; Diéguez, Montserrat

doi:10.1021/acs.orglett.8b04084

Cited by 41 publications

(16 citation statements)

References 25 publications

(15 reference statements)

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“…During the last decade our group has developed several modular P‐stereogenic chiral ligands that have proven to be excellent precursors of chiral catalysts. Although our iridium‐P,N MaxPHOX family of catalysts ( 6 ) have been successfully applied to the asymmetric hydrogenation of cyclic enamides, aryl and alkyl imines, and minimally functionalized olefins, including 2‐aryl N ‐allyl phthalimides, we found that in this particular case, using 3 a as model substrate, [((4 S ,5 S )‐Cy 2 ‐Ubaphox)Ir(COD)]BAr F 4 ( 7 ) gave the best results.…”

Section: Resultsmentioning

confidence: 94%

Catalytic Regioselective Isomerization of 2,2‐Disubstituted Oxetanes to Homoallylic Alcohols

et al. 2020

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The selective isomerization of strained heterocyclic compounds is an important tool in organic synthesis. An unprecedented regioselective isomerization of 2,2‐disubstituted oxetanes into homoallylic alcohols is described. The use of tris(pentafluorophenyl)borane (B(C6F5)3), a commercially available Lewis acid was key to obtaining good yields and selectivities since other Lewis acids afforded mixtures of isomers and substantial polymerization. The reaction took place under exceptionally mild reaction conditions and very low catalyst loading (0.5 mol %). DFT calculations disclose the mechanistic features of the isomerization and account for the high selectivity displayed by the B(C6F5)3 catalyst. The synthetic applicability of the new reaction is demonstrated by the preparation of γ‐chiral alcohols using iridium‐catalyzed asymmetric hydrogenation.

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Section: Resultsmentioning

confidence: 94%

Catalytic Regioselective Isomerization of 2,2‐Disubstituted Oxetanes to Homoallylic Alcohols

et al. 2020

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“…For this family of substrates, catalyst 32b emerged as the most suitable. 45 However, when moving to acyclic olefins, 31b gave the best enantioselectivities (Figure 7). It is remarkable that the distinct diastereomers in the ligand library gave such a diversity of results.…”

Section: Catalysismentioning

confidence: 99%

P-Stereogenic Amino-Phosphines as Chiral Ligands: From Privileged Intermediates to Asymmetric Catalysis

2020

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Conspectus Among chiral phosphines, P-stereogenic phosphines provide unparalleled activity and selectivity and have thus emerged as “state-of-the-art” ligands for asymmetric hydrogenation and other industrially relevant processes. However, the synthesis of this type of ligand implies lengthy multistep sequences, which are a hurdle for many laboratories. There is a lack of methods for the rapid construction of P-stereogenic phosphine ligands. In this respect, P-stereogenic synthons that can be rapidly incorporated into a given ligand scaffold are highly desirable. Over the last 10 years, our group has unveiled that P-stereogenic aminophosphines can be rapidly assembled in a convenient fashion from the corresponding primary aminophosphine and/or the corresponding phosphinous acid. Using cis-1-amino-2-indanol as chiral auxiliary, we devised a multigram synthesis of tert-butylmethylaminophosphine borane and tert-butylmethylphosphinous acid borane, which are key intermediate synthons. Primary aminophosphine works as nucleophilic intermediates at nitrogen. From this synthon, aminodiphosphine (MaxPHOS) and secondary imino phosphoranes (SIP) ligands were synthesized. These ligands exhibit a tautomeric equilibrium between the PH and NH forms, and because of that, they do not undergo oxidation in air. NH/PH tautomerism does not jeopardize their configurational stability, and most importantly, in the presence of a metal source, the equilibrium is shifted toward the NH form, thus allowing coordination through phosphorus. Rh-MaxPHOS and Rh-SIP complexes have been used in asymmetric hydrogenation and [2 + 2 + 2] cycloaddition reactions with outstanding results. On the other hand, P-stereogenic phosphinous acid, upon activation, serves as an electrophilic reagent with amine nucleophiles, allowing SN2 reactions at phosphorus with complete inversion of configuration. This coupling technology exhibits a great potential because it allows the incorporation of the P*-phosphine fragment in numerous ligand structures, provided there is an amino group with which to react. In a mild and efficient process, phosphinous acid has been coupled to hydrazine to yield C 2 diphosphines and to chiral benzoimidazole-amines to yield P-stereogenic benzoimidazole-phosphine ligands. The most powerful ligand system, however, arises from the condensation of three independent fragments: our phosphinous acid borane, an amino acid, and an amino alcohol, which yields a library of phosphino-oxazoline ligands named MaxPHOX. The corresponding Ir-MaxPHOX catalyst library was applied with excellent results in the asymmetric hydrogenation of α,β-unsaturated esters, 2-aryl allyl phthalimides, unfunctionalized tetrasubstituted alkenes, cyclic enamides, and N-aryl and N-methyl imines. It also has found application in asymmetric isomerization of alkenes. Overall, we developed key P-stereogenic building blocks that can be incorporated stereospecifically to ligand scaffolds and demonstrated that integration of the P*-aminophosphine fragment in a given catalytic system p...

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“…To demonstrate that, we moved to perform the asymmetric hydrogenation of the homoallylic alcohols 3,w hich are considered minimally functionalized olefins. [29] During the last decade our group has developed several modular P-stereogenic chiral ligands [30] that have proven to be excellent precursors of chiral catalysts.Although our iridium-P, NM axPHOX [31] family of catalysts (6)h ave been successfully applied to the asymmetric hydrogenation of cyclic enamides, [31a] aryl and alkyl imines, [32] and minimally functionalized olefins, [33] including 2-aryl N-allyl phthalimides, [34] we found that in this particular case,u sing 3a as model substrate,[((4S,5S)-Cy 2 -Ubaphox)Ir(COD)]BAr F 4 (7) [35] gave the best results.…”

Section: Angewandte Chemiementioning

confidence: 99%

Catalytic Regioselective Isomerization of 2,2‐Disubstituted Oxetanes to Homoallylic Alcohols

et al. 2020

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The selective isomerization of strained heterocyclic compounds is an important tool in organic synthesis.A n unprecedented regioselective isomerization of 2,2-disubstituted oxetanes into homoallylic alcohols is described. The use of tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) , ac ommercially available Lewis acid was key to obtaining good yields and selectivities since other Lewis acids afforded mixtures of isomers and substantial polymerization. The reaction took place under exceptionally mild reaction conditions and very low catalyst loading (0.5 mol %). DFT calculations disclose the mechanistic features of the isomerization and account for the high selectivity displayed by the B(C 6 F 5 ) 3 catalyst. The synthetic applicability of the new reaction is demonstrated by the preparation of g-chiral alcohols using iridium-catalyzed asymmetric hydrogenation. Dr.A .C abrØ,S.R afael, Prof. X. Verdaguer,P rof. A. Riera Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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Extending the Substrate Scope in the Hydrogenation of Unfunctionalized Tetrasubstituted Olefins with Ir-P Stereogenic Aminophosphine–Oxazoline Catalysts

Cited by 41 publications

References 25 publications

Catalytic Regioselective Isomerization of 2,2‐Disubstituted Oxetanes to Homoallylic Alcohols

Catalytic Regioselective Isomerization of 2,2‐Disubstituted Oxetanes to Homoallylic Alcohols

P-Stereogenic Amino-Phosphines as Chiral Ligands: From Privileged Intermediates to Asymmetric Catalysis

Catalytic Regioselective Isomerization of 2,2‐Disubstituted Oxetanes to Homoallylic Alcohols

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