Role of quaternary ammonium salts as new additives in the enantioselective organocatalytic β-benzylation of enals

Duce, Sara; Mateo, A; Alonso, Inés; Ruano, José Luis Garcı́a; Cid, M. B.

doi:10.1039/c2cc31451g

Cited by 30 publications

(18 citation statements)

References 31 publications

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“… a–e See the corresponding footnotes in Table 1. f Absolute configuration of the hydrogenated product was tentatively assigned based on specific optical rotation. g Absolute configuration of the hydrogenated product was tentatively assigned on the basis of elution order and specific optical rotation. h Reaction carried out with 1.5 mol % catalyst under 100 bar H 2 . i Reaction carried out under 100 bar H 2 . j Conversion determined by 1 H NMR. k See refs , − , as noted in the table. …”

Section: Resultsmentioning

confidence: 99%

Asymmetric Hydrogenation of Allylic Alcohols Using Ir–N,P-Complexes

Liu

Krajangsri

et al. 2016

ACS Catal.

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In this study, a series of γ,γ-disubstituted and β,γ-disubstituted allylic alcohols were prepared and successfully hydrogenated using suitable N,P-based Ir complexes. High yields and excellent enantioselectivities were obtained for most of the substrates studied. This investigation also revealed the effect of the acidity of the N,P−Ir-complexes on the acidsensitive allylic alcohols. DFT ΔpK a calculations were used to explain the effect of the N,P-ligand on the acidity of the corresponding Ir-complex. The selectivity model of the reaction was used to accurately predict the absolute configuration of the hydrogenated alcohols.

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Section: Resultsmentioning

confidence: 99%

Asymmetric Hydrogenation of Allylic Alcohols Using Ir–N,P-Complexes

Liu

Krajangsri

et al. 2016

ACS Catal.

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“…Without n -Bu 4 NOAc, 4a was not obtained at all, and nor was the C-H olefinated product ( 3a ) formed. Quaternary ammonium salts have always been considered to be an effective catalyst for Michael reactions [ 74 , 75 , 76 , 77 , 78 , 79 ]. As one can see from Figure 2 , the intramolecular aza-Michael reaction of ortho -alkenylated-2-phenyl-1 H -indole could indeed be improved by the addition of n -Bu 4 NOAc.…”

Section: Resultsmentioning

confidence: 99%

Rhodium-Catalyzed Oxidative Annulation of 2- or 7-Arylindoles with Alkenes/Alkynes Using Molecular Oxygen as the Sole Oxidant Enabled by Quaternary Ammonium Salt

et al. 2021

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Developing an efficient catalytic system using molecular oxygen as the oxidant for rhodium-catalyzed cross-dehydrogenative coupling remains highly desirable. Herein, rhodium-catalyzed oxidative annulation of 2- or 7-phenyl-1H-indoles with alkenes or alkynes to assemble valuable 6H-isoindolo[2,1-a]indoles, pyrrolo[3,2,1-de]phenanthridines, or indolo[2,1-a]isoquinolines using the atmospheric pressure of air as the sole oxidant enabled by quaternary ammonium salt has been accomplished. Mechanistic studies provided evidence for the fast intramolecular aza-Michael reaction and aerobic reoxidation of Rh(I)/Rh(III), facilitated by the addition of quaternary ammonium salt.

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“…Again, the product was isolated as a mixture of enol/keto forms (∼3:1 ratio; only the enol form is shown for clarity). To improve the reaction, a series of additives (BzOH, TBAB, NaHCO 3 , LiOAc) were investigated, with significantly improved yields being obtained with the LiOAc (Table , entry 3). The use of water as an additive (10 equiv) led to both an increase in yield and ee (Table , entry 7).…”

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confidence: 93%