Asymmetric synthesis based on chiral (arene)tricarbonylchromium acetal complexes. Addition reactions to the ortho-formyl complex

2000 ◽  
Vol 78 (12) ◽  
pp. 1629-1636 ◽  
Author(s):  
M Kevin McKay ◽  
James R Green
Keyword(s):  
Asymmetric Synthesis ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Nucleophilic Attack ◽  
Addition Reactions ◽  
Trans Conformation ◽  
Enantiomerically Pure ◽  
The Face ◽  
Monodentate Coordination ◽  
Tricarbonylchromium Complexes

The addition reactions of organolithium and Grignard reagents to chiral, enantiomerically pure ortho-formyl (arene)tricarbonylchromium acetal complex (2) have been studied. The diastereoselectivity of the addition process is fair in the absence of an additional Lewis acid, and good in the presence of Ti(OiPr)4. The nature of the newly formed chiral centre, and studies on the possible nature of the nucleophilic species suggest that the Lewis acid acts through monodentate coordination to the aldehyde carbonyl, and thereby alters the carbonyl rotamer population more heavily in favour of the s-trans conformation. Nucleophilic attack then occurs on the face anti- to that bearing the Cr(CO)3 unit.Key words: (arene)tricarbonylchromium complexes, asymmetric synthesis, carbonyl additions, Lewis acids.

Bidentate Lewis acid catalysts in asymmetric synthesis

2002 ◽  
Vol 74 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Keiji Maruoka
Keyword(s):  
Asymmetric Synthesis ◽  
Organic Synthesis ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Asymmetric Induction ◽  
Acid Catalysts ◽  
Lewis Acid Catalysts ◽  
High Chemical ◽  
Bidentate Lewis Acids

The chemistry of bidentate Lewis acids belongs to an unexplored field of science, and so far has been only poorly studied. This paper illustrates the design of several bidentate Al and Ti Lewis acids, and their successful application to selective organic synthesis, particularly to asymmetric synthesis. For example, a new, chiral bidentate Ti(IV) complex is successfully designed by adding commercially available Ti(OPri)4 and (S)-binaphthol sequentially to 2,2'-bis(tritylamino)-4,4'-dichlorobenzophenone in CH2Cl2, and can be utilized for simultaneous coordination to aldehyde carbonyls, thereby allowing the precise enantioface discrimination of such carbonyls for a new catalytic, practical enantioselective allylation of aldehydes with allyltributyltin. This chiral bidentate Ti(IV) catalyst exhibits uniformly high asymmetric induction as well as high chemical yields for various aldehydes. The present enantioselective allylation is highly chemoselective in the presence of other carbonyl moieties.

scholarly journals Amphoteric Lewis Acid/base Activity Enables an Unprecedented Pathway for Low-Energy C-O Cleavage in the Electrocatalytic Reduction of Carbon Dioxide

2021 ◽  
Author(s):  
Hemlata Agarwala ◽  
Xiaoyu Chen ◽  
Julien R. Lyonnet ◽  
Ben A Johnson ◽  
Mårten Ahlquist ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Density Functional ◽  
Activation Barrier ◽  
Bond Cleavage ◽  
Lewis Base ◽  
Nucleophilic Attack ◽  
Co Conversion ◽  
Energy Conserving ◽  
Ft Ir

Molecular electrocatalysts for CO<sub>2</sub>-to-CO conversion often operate at large overpotentials, the cleavage of C-O bond in the intermediate largely contributing to this phenomenon. Additional Lewis acids have been shown to aid in weakening the C-O bond. We herein present computational and experimental evidence, with ruthenium polypyridyl based CO<sub>2</sub> reduction electrocatalysts, for a mechanistic route that involves one metal center acting as both Lewis base and Lewis acid at different stages of the catalytic cycle. The Lewis basic character of Ru is seen in the initial nucleophilic attack at CO<sub>2</sub> to form [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup>, while its Lewis acid character allows the formation of a 5-membered metallacyclic intermediate, [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup>, by intramolecular cyclization of a linear [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup> species that is formed from [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup> and a second equivalent of CO<sub>2</sub>. [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup> is crucial for energy-conserving turnover, as it allows for a third reduction at a more positive potential than that of the starting complex <b>Ru</b><sup>2+</sup>. The calculated activation barrier for C-O bond cleavage in [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>-1,c</sup> is dramatically decreased to 10.5 kcal mol<sup>-1</sup> from 60 kcal mol<sup>-1</sup>, the latter required for C-O bond cleavage in the linear intermediate [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup>. The intermediates are characterized experimentally by FT-IR and <sup>13</sup>C NMR spectroscopy during electrocatalytic turnover and are corroborated by density functional theory (DFT).<br>

Asymmetric synthesis by stereocontrol

2001 ◽  
Vol 73 (2) ◽  
pp. 283-286 ◽  
Author(s):  
Yong Hae Kim ◽  
Sam Min Kim ◽  
So Won Youn
Keyword(s):  
Asymmetric Synthesis ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Diels Alder ◽  
Samarium Diiodide ◽  
Coupling Reactions ◽  
Pinacol Coupling

Diels-Alder cycloadditions of S-indoline chiral acrylamides with cyclopentadiene in the presence of Lewis acids proceed with high diastereofacial selectivity, giving either endo-R or endo-S products depending on Lewis acid and the structures of chiral dienophiles. Diastereo- and enantioselective pinacol coupling reactions of chiral α-ketoamides mediated by samarium diiodide afforded extremely high diastereoselectivities. Enantiopure (S,S) - or (R,R) -2,3-dialkyltartaric acid and derivatives can be synthesized. Furthermore, it was demonstrated that α,β-unsaturated amides coupled with SmI2 to dimerized products containing two chiral carbons which were first obtained as the adjacent chiral carbons.

scholarly journals Amphoteric Lewis Acid/base Activity Enables an Unprecedented Pathway for Low-Energy C-O Cleavage in the Electrocatalytic Reduction of Carbon Dioxide

2021 ◽  
Author(s):  
Hemlata Agarwala ◽  
Xiaoyu Chen ◽  
Julien R. Lyonnet ◽  
Ben A Johnson ◽  
Mårten Ahlquist ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Density Functional ◽  
Activation Barrier ◽  
Bond Cleavage ◽  
Lewis Base ◽  
Nucleophilic Attack ◽  
Co Conversion ◽  
Energy Conserving ◽  
Ft Ir

Molecular electrocatalysts for CO<sub>2</sub>-to-CO conversion often operate at large overpotentials, the cleavage of C-O bond in the intermediate largely contributing to this phenomenon. Additional Lewis acids have been shown to aid in weakening the C-O bond. We herein present computational and experimental evidence, with ruthenium polypyridyl based CO<sub>2</sub> reduction electrocatalysts, for a mechanistic route that involves one metal center acting as both Lewis base and Lewis acid at different stages of the catalytic cycle. The Lewis basic character of Ru is seen in the initial nucleophilic attack at CO<sub>2</sub> to form [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup>, while its Lewis acid character allows the formation of a 5-membered metallacyclic intermediate, [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup>, by intramolecular cyclization of a linear [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup> species that is formed from [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup> and a second equivalent of CO<sub>2</sub>. [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup> is crucial for energy-conserving turnover, as it allows for a third reduction at a more positive potential than that of the starting complex <b>Ru</b><sup>2+</sup>. The calculated activation barrier for C-O bond cleavage in [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>-1,c</sup> is dramatically decreased to 10.5 kcal mol<sup>-1</sup> from 60 kcal mol<sup>-1</sup>, the latter required for C-O bond cleavage in the linear intermediate [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup>. The intermediates are characterized experimentally by FT-IR and <sup>13</sup>C NMR spectroscopy during electrocatalytic turnover and are corroborated by density functional theory (DFT).<br>

scholarly journals Alternating substrate/ligand-metal coordination enables a low-energy pathway for C-O bond cleavage in the electrocatalytic reduction of carbon dioxide

2021 ◽  
Author(s):  
Hemlata Agarwala ◽  
Xiaoyu Chen ◽  
Julien R. Lyonnet ◽  
Ben A Johnson ◽  
Mårten Ahlquist ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Density Functional ◽  
Activation Barrier ◽  
Bond Cleavage ◽  
Lewis Base ◽  
Nucleophilic Attack ◽  
Co Conversion ◽  
Energy Conserving ◽  
Ft Ir

Molecular electrocatalysts for CO<sub>2</sub>-to-CO conversion often operate at large overpotentials, the cleavage of C-O bond in the intermediate largely contributing to this phenomenon. Additional Lewis acids have been shown to aid in weakening the C-O bond. We herein present computational and experimental evidence, with ruthenium polypyridyl based CO<sub>2</sub> reduction electrocatalysts, for a mechanistic route that involves one metal center acting as both Lewis base and Lewis acid at different stages of the catalytic cycle. The Lewis basic character of Ru is seen in the initial nucleophilic attack at CO<sub>2</sub> to form [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup>, while its Lewis acid character allows the formation of a 5-membered metallacyclic intermediate, [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup>, by intramolecular cyclization of a linear [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup> species that is formed from [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup> and a second equivalent of CO<sub>2</sub>. [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup> is crucial for energy-conserving turnover, as it allows for a third reduction at a more positive potential than that of the starting complex <b>Ru</b><sup>2+</sup>. The calculated activation barrier for C-O bond cleavage in [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>-1,c</sup> is dramatically decreased to 10.5 kcal mol<sup>-1</sup> from 60 kcal mol<sup>-1</sup>, the latter required for C-O bond cleavage in the linear intermediate [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup>. The intermediates are characterized experimentally by FT-IR and <sup>13</sup>C NMR spectroscopy during electrocatalytic turnover and are corroborated by density functional theory (DFT).<br>

Indium Bromide-catalyzed Unprecedented Hydrogenolysis: A Novel One-Pot Synthesis of Per-O-Acetylated β-carboxymethyl O and S-glycosides

2020 ◽  
Vol 24 (8) ◽  
pp. 900-908
Author(s):  
Ram Naresh Yadav ◽  
Amrendra K Singh ◽  
Bimal Banik
Keyword(s):  
Asymmetric Synthesis ◽  
Chiral Auxiliary ◽  
Bioactive Molecules ◽  
One Pot ◽  
Enantiomerically Pure ◽  
Stereoselective Glycosylation ◽  
One Pot Synthesis ◽  
Wide Range

Numerous O (oxa)- and S (thia)-glycosyl esters and their analogous glycosyl acids have been accomplished through stereoselective glycosylation of various peracetylated bromo sugar with benzyl glycolate using InBr3 as a glycosyl promotor followed by in situ hydrogenolysis of resulting glycosyl ester. A tandem glycosylating and hydrogenolytic activity of InBr3 has been successfully investigated in a one-pot procedure. The resulting synthetically valuable and virtually unexplored class of β-CMGL (glycosyl acids) could serve as an excellent potential chiral auxiliary in the asymmetric synthesis of a wide range of enantiomerically pure medicinally prevalent β-lactams and other bioactive molecules of diverse medicinal interest.

Stereochemistry of epoxide carbonylation using bimetallic Lewis acid/metal carbonyl complexes

2004 ◽  
Vol 76 (3) ◽  
pp. 557-564 ◽  
Author(s):  
Y. D. Y. L. Getzler ◽  
Viswanath Mahadevan ◽  
E. B. Lobkovsky ◽  
G. W. Coates
Keyword(s):  
Lewis Acid ◽  
Kinetic Resolution ◽  
Metal Carbonyl ◽  
Carbonyl Complexes ◽  
Enantiomerically Pure ◽  
Metal Carbonyl Complexes ◽  
Pure Complex

The stereochemistry of epoxide carbonylation using bimetallic [Lewis acid]+[Co(CO)4]- complexes is reported. The achiral complex [(salph)Al(THF)2][Co(CO)4] stereospecifically carbonylates cis- and trans-2-butene oxide to the trans- and cis-β-lactones, respectively. Preliminary experiments regarding the carbonylative kinetic resolution of racemic trans-2-butene oxide using the enantiomerically pure complex [(R,R-salcy)Al(THF)2][Co(CO)4] are also reported.

Asymmetric synthesis of N-phenylethyl-2-phenyldecahydroquinolin-4-ones via Lewis acid catalyzed imino-Diels–Alder reaction

2000 ◽  
Vol 11 (12) ◽  
pp. 2509-2523 ◽  
Author(s):  
Renée Paugam ◽  
Emmanuelle Valenciennes ◽  
Linda Le Coz-Bardol ◽  
Jean-Christophe Garde ◽  
Lya Wartski ◽  
...  
Keyword(s):  
Asymmetric Synthesis ◽  
Lewis Acid ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Acid Catalyzed

Asymmetric synthesis of isoquinuclidines by Diels–Alder reaction of 1,2-dihydropyridine utilizing a chiral Lewis acid catalyst

Tetrahedron ◽  
2012 ◽  
Vol 68 (6) ◽  
pp. 1774-1781 ◽  
Author(s):  
Chigusa Seki ◽  
Masafumi Hirama ◽  
N.D.M. Romauli Hutabarat ◽  
Junko Takada ◽  
Chonticha Suttibut ◽  
...  
Keyword(s):  
Asymmetric Synthesis ◽  
Lewis Acid ◽  
Acid Catalyst ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Chiral Lewis Acid ◽  
Lewis Acid Catalyst
Sign in / Sign up

Export Citation Format

Share Document