Enantioselective catalytic rearrangement of cyclohexene oxide with new homochiral bis-lithium amide bases

Equey, Olivier; Alexakis, Alexandre

doi:10.1016/j.tetasy.2004.02.030

Cited by 15 publications

(4 citation statements)

References 25 publications

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“…Synthesis of the ligand precursors began with the preparation of chiral diamines 6 − 8 of Scheme , followed by their condensation with triethyl orthoformate and ammonium tetrafluoroborate to give the corresponding 4,5-dihydroimidazolium salts 9 − 11 . These salts were treated with potassium hexafluoro- tert -butoxide and (PCy) 3 (Cl) 2 RuCHPh to afford the desired chiral complexes 3 − 5 in around 40% yield …”

Section: Resultsmentioning

confidence: 99%

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Ruthenium-Based Complexes Bearing Saturated Chiral N-Heterocyclic Carbene Ligands: Dynamic Behavior and Catalysis

et al. 2008

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The synthesis of Ru-based catalysts, presenting saturated chiral C 2 symmetric (3, 5) and C 1 symmetric (4) N-heterocyclic carbene (NHC) ligands bearing N-(S)-phenylethyl groups, was carried out. Variable-temperature NMR studies were conducted to investigate the interconversion of atropisomers in solution. The complex behaviors were rationalized evaluating the rotation barrier of alkylidene and NHC groups around the C−Ru bonds, by DFT calculations. Comparison between NMR data and DFT calculations suggested that interconversion between different atropisomers, which occurs at room temperature, is due to the free rotation of the benzylidene group around the RuC bond. The activity and stereoselectivity of 3−5 were investigated in ring-closing metathesis (RCM), asymmetric ring-closing metathesis (ARCM), cross-metathesis (CM), and ring-opening metathesis polymerization (ROMP). 4 showed the highest activity in all reactions and gave a significantly low E:Z ratio in the CM reaction. Modest enantioselectivity in the ARCM of an achiral triene was observed in the presence of C 2 symmetric catalyst 5.

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Section: Resultsmentioning

confidence: 99%

“…These products were used without further purification. The syntheses of diamines 4a , 4b , and 4c were effected by reported procedures . Triene 18 was prepared as previously reported .…”

Section: Methodsmentioning

confidence: 99%

Ruthenium-Based Complexes Bearing Saturated Chiral N-Heterocyclic Carbene Ligands: Dynamic Behavior and Catalysis

et al. 2008

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“…Results of comparative rearrangement reactions performed with diamines having modified carbon chain tethers and substituents (diamines 17 − 21 ) are shown in Table . , In summary, diamine 17 having a three carbon linker, provided 3b with the highest enantiomeric excess. The findings that the enantioselectivity could be optimized by changing the size of the carbon chain linker and that the replacement of one secondary amine of the diamine with a tertiary amine (diamine 19 ) gave essentially racemic 3b are consistent with the bidentate chelation model shown in Scheme .…”

Section: Resultsmentioning

confidence: 99%

Design, Development, and Scale-Up of a Selective meso-Epoxide Desymmetrization Process

Varie¹,

Beck²,

Borders³

et al. 2007

Org. Process Res. Dev.

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A pilot-plant scale desymmetrization of the cyclic meso-epoxide 4b, using a chiral lithium amide prepared from symmetrical diamine 17, was designed and implemented to provide allylic alcohol 3b in high yield and greater than 99% ee. This chiral alcohol was converted to ketone 2b, a key intermediate in a new asymmetric synthesis of LY459477. Chiral diamine 17 was prepared from a readily available chiral precursor, (R)-rmethylbenzylamine, and could be recovered from the reaction mixture and reused. Studies performed to probe the mechanism of the rearrangement reaction of epoxide 4b showed that diamine 17 provided an optimal combination of selectivity and scaleability for this process.

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“…The (S,S) isomer of N,N 0 -bis[1-phenylethyl]-1,3-diaminopropane (3) was previously synthesized and characterized by Feringa and co-workers [33]. Reactions of the (S,S) isomer of N,N 0 -bis [1-(1-naphthyl)ethyl]-1,3-diaminopropane (4) have been reported by Equey and Alexakis, but no details of synthesis and characterization were provided [34].…”

Section: Synthesis Of Chiral Diaminesmentioning

confidence: 99%

Palladium complexes of bis(acyclic diaminocarbene) ligands with chiral N-substituents and 8-membered chelate rings

Wanniarachchi

Subramanium

Slaughter

2009

Journal of Organometallic Chemistry

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Enantioselective catalytic rearrangement of cyclohexene oxide with new homochiral bis-lithium amide bases

Cited by 15 publications

References 25 publications

Ruthenium-Based Complexes Bearing Saturated Chiral N-Heterocyclic Carbene Ligands: Dynamic Behavior and Catalysis

Ruthenium-Based Complexes Bearing Saturated Chiral N-Heterocyclic Carbene Ligands: Dynamic Behavior and Catalysis

Design, Development, and Scale-Up of a Selective meso-Epoxide Desymmetrization Process

Palladium complexes of bis(acyclic diaminocarbene) ligands with chiral N-substituents and 8-membered chelate rings

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