Chiral relay in NHC-mediated asymmetric β-lactam synthesis I; substituent effects in NHCs derived from (1R,2R)-cyclohexane-1,2-diamine

Duguet, Nicolas; Donaldson, Adele; Leckie, Stuart M.; Douglas, James J.; Shapland, Peter; Brown, T. Bruce; Churchill, Gwydion H.; Slawin, Alexandra M. Z.; Smith, Andrew D.

doi:10.1016/j.tetasy.2010.03.001

Cited by 42 publications

(15 citation statements)

References 117 publications

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“…Recourse to racemic C 2 ‐symmetric N , N′ ‐dibenzyl or N , N′ ‐dimethyl imidazolinium salts CySIBn ⋅ HBF 4 and CySIMe ⋅ HBF 4 derived from ( ± )‐ trans ‐cyclohexane‐1,2‐diamine led to the formation of β‐lactam 6 in high yield and with moderate diastereoselectivity in favor of the cis isomer (Table 2, entries 1 and 2). These results corroborate previous observations from Smith et al., who first synthesized these two catalyst precursors in optically active forms and probed their activity in asymmetric Staudinger reactions 17a. The presence of exocyclic methylene or methyl groups on the nitrogen atoms of these NHCs ensures minimal steric hindrance on the α positions of the N substituents, which may be invoked to justify a cis / trans ratio close to 50:50.…”

Section: Resultssupporting

confidence: 89%

Probing the Diastereoselectivity of Staudinger Reactions Catalyzed by N‐Heterocyclic Carbenes

Hans

Demonceau

Delaude

2015

Chemistry A European J

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The reaction of ethylphenylketene with 1,3-dimesitylimidazol-2-ylidene (IMes) or 1,3-dimesitylimidazolin-2-ylidene (SIMes) afforded the corresponding azolium enolates in high yields. The two zwitterions were fully characterized by various analytical techniques. Their thermal stabilities were monitored by thermogravimetric analysis and the molecular structure of SIMes⋅EtPhCCO was determined by means of X-ray crystallography. A mechanism was proposed to account for the trans-diastereoselectivity observed in the [2+2] cycloaddition of ketenes and N-protected imines catalyzed by N-heterocyclic carbenes and an extensive catalytic screening was performed to test its validity. The steric bulk of the NHC catalyst markedly affected the cis/trans ratio of the model β-lactam product. The nature of the solvent used to carry out the Staudinger reaction also significantly influenced its diastereoselectivity. Conversely, the nature of the substituent on the N-sulfonated imine reagent and the reaction temperature were less critical parameters.

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Section: Resultssupporting

confidence: 89%

Probing the Diastereoselectivity of Staudinger Reactions Catalyzed by N‐Heterocyclic Carbenes

Hans

Demonceau

Delaude

2015

Chemistry A European J

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“…( R , R )‐1,2‐Diaminocyclohexane (= (1 R ,2 R )‐Cyclohexane‐1,2‐diamine ; ( R , R )‐DACH) . This compound (3.14 g, 27.5 mmol, 91%) was obtained from ( R , R )‐cyclohexane‐1,2‐diammonium ( R,R )‐tartrate (8.00 g, 30.3 mmol, 1.0 equiv.)…”

Section: Methodsmentioning

confidence: 99%

Configurational Assignment of ‘Cryptochiral’ 10‐Hydroxystearic Acid Through an Asymmetric Catalytic Synthesis

Brunner

Hintermann

2016

Helvetica Chimica Acta

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An asymmetric catalytic total synthesis of (S)‐10‐hydroxystearic acid (1) for comparison of its absolute configuration to that of samples obtained by fermentative hydration of oleic acid is reported. The synthesis involves two catalytic key‐steps, namely Ru‐catalyzed anti‐Markovnikov hydration of 9‐decynoic acid (7) to 10‐oxodecanoic acid (5), followed by titanium‐mediated asymmetric catalytic addition of dioctylzinc (25) to 5 in presence of the chiral ligand N,N’‐((1R,2R)‐cyclohexane‐1,2‐diyl)bis(1,1,1‐trifluoromethanesulfonamide) (6). The synthesis is short and efficient and avoids use of protecting groups. Ozonolysis of 10‐undecynoic acid (9) to 5 provides an alternative entry point into the synthetic route. The double dehydrobromination of (ω,ω‐1)‐dibromoalkanoic acids to ω‐alkynoic acids under a variety of conditions was investigated with 10,11‐dibromoundecanoic acid (11) as model substrate and using qNMR to quantify all reaction products. The synthetic approaches presented here have the potential to be generalized to the asymmetric catalytic synthesis of a variety of n‐hydroxy‐fatty acids.

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“…However, usually this is a reaction that needs catalysis. [35][36][37] Among the catalysts, NHCs have been recently used in the Staudinger synthesis [10,16,17,[38][39][40] starting from highly electrophilic imines (e.g., N-Boc, N-Ts and N-pNs imines). These reactions are successfully carried out in classical VOCs, using a disubstituted ketene (pre-prepared) and an electrophilic imine, in the presence of an NHC as organocatalyst.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Role of Electrogenerated N-Heterocyclic Carbene in the Staudinger Synthesis in Ionic Liquid

Feroci¹

2011

IJOC

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Electrogenerated N-heterocyclic carbene (NHC), obtained by cathodic reduction of Bmim-BF 4 , behaves as organocatalyst and base in the Staudinger synthesis from an acyl chloride and a deactivated imine in ionic liquid to yield -lactams. The effect of many parameters (temperature, amount of electricity, substituents, presence of an external base) has been evaluated and a tentative mechanism for the Staudinger synthesis in a very polar medium like the ionic liquid reported. The yields of isolated -lactams are good, starting from non-electrophilic imines, and predominantly trans lactams are obtained with a good diastereomeric ratio.

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Chiral relay in NHC-mediated asymmetric β-lactam synthesis I; substituent effects in NHCs derived from (1R,2R)-cyclohexane-1,2-diamine

Cited by 42 publications

References 117 publications

Probing the Diastereoselectivity of Staudinger Reactions Catalyzed by N‐Heterocyclic Carbenes

Probing the Diastereoselectivity of Staudinger Reactions Catalyzed by N‐Heterocyclic Carbenes

Configurational Assignment of ‘Cryptochiral’ 10‐Hydroxystearic Acid Through an Asymmetric Catalytic Synthesis

Investigation of the Role of Electrogenerated N-Heterocyclic Carbene in the Staudinger Synthesis in Ionic Liquid

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