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| 2. |
- Naicker, Tricia, et al.
(författare)
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Microwave-Assisted Synthesis of Guanidine Organocatalysts Bearing a Tetrahydroisoquinoline Framework and Their Evaluation in Michael Addition Reactions
- 2012
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :17, s. 3331-3337
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Tidskriftsartikel (refereegranskat)abstract
- The simple and practical syntheses of chiral guanidine organocatalysts and their evaluation in the asymmetric Michael addition reaction of malonates and beta-keto esters with nitro-olefins is reported. These organocatalysts are the first of their kind based on a tetrahydroisoquinoline framework. In addition, a microwave-assisted procedure for introducing the guanidine unit onto amino amide derivatives is reported. The chiral products were obtained with quantitative chemical efficiency (up to 99 % yield) and excellent enantioselectivity (up to 97 % ee).
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| 3. |
- Naicker, Tricia, et al.
(författare)
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Novel tetrahydroisoquinoline based organocatalysts for asymmetric Diels–Alder reactions : insight into the catalytic mode using ROESY NMR and DFT studies
- 2010
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Ingår i: Tetrahedron. - : Elsevier BV. - 0957-4166 .- 1362-511X. ; 21:23, s. 2859-2867
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Tidskriftsartikel (refereegranskat)abstract
- For the first time an organocatalyst bearing a secondary nitrogen within a cyclohexane ring has been evaluated in the asymmetric Diels–Alder reaction. This organocatalyst is also the first of its kind based on a (1R,3S)-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline backbone. These catalysts were tested over a range of dienes and dienophiles and displayed promising chemical conversions of up to 100% with up to 64% ee with triflic acid as the cocatalyst. Density functional theory computational studies and 2D NMR spectroscopy were used to determine the structure of the intermediate iminium ion formed between the most efficient catalyst and cinnamaldehyde. The reaction profile for each of the four possibilities in this reaction were calculated and it was found that the iminium intermediate leading to the major product is higher in energy but kinetically preferred. The activation energies of all possible reaction paths were calculated and the results correlated with the observed products. These experiments revealed that the presence of both (E)- and (Z)-isomers of the cinnamaldehyde were contributing factors for the low enantioselectivity of the reaction products.
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| 4. |
- Naicker, Tricia, et al.
(författare)
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Tetrahydroisoquinoline-Based N-Oxides as Chiral Organocatalysts for the Asymmetric Allylation of Aldehydes
- 2011
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 2011:34, s. 6923-6932
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Tidskriftsartikel (refereegranskat)abstract
- The short synthesis of a series of novel chiral N-oxideorganocatalysts and their evaluation in the asymmetric allylation reaction of aromatic and α-β-unsaturated aldehydes with allyltrichlorosilane is reported. These readily modifiable organocatalysts are the first of their kind based on the tetrahydroisoquinoline framework. The chiral homoallyl products were obtained with good chemical efficiency (up to 93 % yield) and high enantioselectivity (up to 91 % ee) under mild reaction conditions (23 °C).
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| 5. |
- Nandi, Ganesh C., et al.
(författare)
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Pd-catalyzed C-N coupling of vinylbromides and sulfonimidamides : a facile synthesis of N '-vinylsulfonimidamides
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:76, s. 62084-62090
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Tidskriftsartikel (refereegranskat)abstract
- N'-Vinyl sulfonimidamides have been synthesized through a Pd-catalyzed C-N cross coupling between the N'-(imine nitrogen) of N'-deprotected sulfonimidamides and vinyl bromides. The hitherto unreported products were obtained in moderate to excellent yield, and the C-C double bond geometry of the vinylic substrates were retained during the course of reaction. Single crystal X-ray crystallographic analysis confirmed the product structure. Furthermore, we demonstrate that the formed N'-vinyl sulfonimidamides could undergo hydrogenation with Pd-C/H-2 to provide N'-alkyl sulfonimidamides.
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| 6. |
- Peters, Byron K., et al.
(författare)
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Synthesis of tetrahydroisoquinoline-diamine ligands and their application in asymmetric transfer hydrogenation
- 2010
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Ingår i: Tetrahedron. - : Elsevier BV. - 0957-4166 .- 1362-511X. ; 21:6, s. 679-687
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Tidskriftsartikel (refereegranskat)abstract
- The use of the tetrahydroisoquinoline scaffold is well documented in biologically active compounds. However, reports of the utilisation of tetrahydroisoquinoline compounds in asymmetric catalysis are limited. The synthesis of novel diamine ligands possessing the tetrahydroisoquinoline (tetrahydroisoquinoline) backbone and evaluation of their activity in the asymmetric transfer hydrogenation of acetophenone are presented. The diamine ligands in conjunction with i-PrOH as the hydrogen source and [RhCl2(Cp*)](2) as the metal precursor proved to be the most effective of the tetrahydroisoquinoline derivatives for this catalytic system. Water was found to have a profound influence on the enantioselectivity of the reaction. Optimisation of the amount water, i-PrOH and catalytic loading content rendered the best result of 70% enantioselectivity for the (S)-1-phenylethanol isomer product.
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