Ultrasound-Assisted Cleavage of N-N Bonds in Hydrazines by Raney Nickel

Alexakis, Alexandre; Lensen, Nathalie; Mangeney, Pierre

doi:10.1055/s-1991-20818

Cited by 54 publications

(14 citation statements)

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“…Reduction with Raney Nickel [43] even with ultrasound activation led to the recovery of starting material 31 a. Only one sulfonyl group was reductively cleaved with aluminium amalgam (Al/Hg) [44] in 75 % conversion after 5 d. Seemingly, these reducing reagents were not suitable for totally removing non-activated geminal bisA C H T U N G T R E N N U N G (sulfones).…”

Section: Determination Of the Ee Of G-gem-phosphonate Aldehydesmentioning

confidence: 99%

Enantioselective Organocatalytic Conjugate Addition of Aldehydes to Vinyl Sulfones and Vinyl Phosphonates as Challenging Michael Acceptors

Sulzer‐Mossé

Alexakis

Mareda

et al. 2009

Chemistry A European J

160

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Chiral framework: Chiral amines with pyrrolidine frameworks catalyze the enantioselective conjugate addition of a wide range of aldehydes to various vinyl sulfones and vinyl phosphonates in high yields and with enantioselectivities up to >99 % ee (see scheme). The high versatility of the Michael adducts is exemplified by various functionalizations with conservation of the optical purity.Chiral amines with a pyrrolidine framework catalyze the enantioselective conjugate addition of a broad range of aldehydes to various vinyl sulfones and vinyl phosphonates in high yields and with enantioselectivities up to >99 % ee. This novel process provides synthetically useful chiral gamma-gem-sulfonyl or phosphonyl aldehydes which can be widely functionalized with retention of the enantiomeric excess. Mechanistic insights including DFT calculations are explored in detail.

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Section: Determination Of the Ee Of G-gem-phosphonate Aldehydesmentioning

confidence: 99%

Enantioselective Organocatalytic Conjugate Addition of Aldehydes to Vinyl Sulfones and Vinyl Phosphonates as Challenging Michael Acceptors

Sulzer‐Mossé

Alexakis

Mareda

et al. 2009

Chemistry A European J

160

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“…Reductive cleavage of the nitrogenϪnitrogen bond of the hydrazino compounds was successfully carried out using Raney Ni under H 2 [49] to afford the β-amino esters. Cyclization of β-NЈ-ben-…”

Section: Mannich-type Reactions Using Hydrazonesmentioning

confidence: 99%

Scandium Triflate in Organic Synthesis

1999

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Sc(OTf)3 is a new type of a Lewis acid that is different from typical Lewis acids such as AlCl3, BF3, SnCl4, etc. While most Lewis acids are decomposed or deactivated in the presence of water, Sc(OTf)3 is stable and works as a Lewis acid in water solutions. Many nitrogen‐containing compounds such as imines and hydrazones are also successfully activated by using a small amount of Sc(OTf)3 in both organic and aqueous solvents. In addition, Sc(OTf)3 can be recovered after reactions are completed and can be reused. While lanthanide triflates [Ln(OTf)3] have similar properties, the catalytic activity of Sc(OTf)3 is higher than that of Ln(OTf)3 in several cases.

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“…The hydroxyl function was first protected as t-butyldimethylsilyl ether because we noticed that no cleavage of the N-N bond could be perfomed in the presence of a free alcohol. After hydrogenolysis of the benzyl carbamates (H 2 , Pd/C), classical conditions such as H 2 , PtO 2 (21) or H 2 , Raney Ni under ultrasounds (22) were used to generate the amine, but degradation of the substrate was observed and no product could be isolated. Then, we tried to deprotect and cleave the hydrazine simultaneously : 10 was exposed to H 2 in presence of PtO 2 .H 2 O in methanol and 45% of the α-aminoester 11 was recovered after flash chromatography.…”

Section: Methodsmentioning

confidence: 99%

Rapid Asymmetric Synthesis of Highly Functionalized C5 Chiral Synthons. Practical Preparation of trans-3-Hydroxy-D-Proline

Poupardin¹,

Greck²,

Genêt³

1998

Synlett

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A stereocontrolled synthesis of (2R, 3R)-3-hydroxyproline 5 has been achieved in 33% overall yield from a prochiral β-ketoester : the methyl 5,5-dimethoxy-3-oxopentanoate 6. The key intermediate is the richly functionalized compound 4 which presented three different oxygenated groups and an anti relationship between the alcohol and the amine.Peptide structures with proline components have received considerable attention over the past few years. (1) trans-3-Hydroxy-L-proline 1 is a constituent of naturally occurring peptides such as Mucrorin-D, (2) Telomycin (3) and has been isolated from mediterranean sponge and from collagen hydrolysates. (4) The reduced form of 1, the trans-3-hydroxy-L-prolinol 2, occurs in the seeds of the legume Castanospernum australe. (5) Scheme 1Several syntheses of trans-3-hydroxyproline and prolinol have been developed in the literature starting from chiral sources such as pyroglutamic acid, (6) L-serine (7) , D-mannitol (8) or L-malic acid. (9) The key intermediates of our approach are the anti diastereomers 3 and 4 of the methyl 2-amino-3-hydroxy-5,5-dimethoxypentanoate. These richly functionalized compounds should be useful for the synthesis of various α-amino-β-hydroxy acids of either (L) or (D) configurations. Scheme 2Recently, Ciufolini et al. reported the synthesis of the N,O diprotected 4 using the Aza-Achmatowicz reaction (10) in several steps from a chiral furan oxazalone. (11) In connection to our continued work on the asymmetric synthesis of α-amino-β-hydroxy acids, our route to 3 and 4 relied on sequential catalytic hydrogenation and electrophilic amination, (12) we report here a concise and stereoselective synthesis of the unnatural trans-3-hydroxy-D-proline.(2R, 3R)-Hydroxyproline 5 was obtained by cyclisation of 4 prepared from β-ketoester 6. (13) First, we studied the hydrogenation of 6 in the presence of ruthenium catalysts. The C5 acetal functionalized β-ketoester 6 presented two symmetrical oxygens in γ positions to the carbonyl group : this could modify the chelation of the ruthenium complex and influence the enantioselectivity of the reaction.Under classical conditions (20 bars, 50°C) the asymmetric hydrogenation of the β-ketoester 6 was carried out in presence of (R)-BinapRuBr 2 (14) or [(R)-BinapRuCl 2 ] 2 -Et 3 N (15) and methanol was used as solvent to avoid secondary reactions such as transacetalisation or transesterification. The yields did not exceed 50% and substantial degradation of the substrate was observed. Then, the hydrogenation was performed at room temperature and atmospheric pressure using 2 molecular % of (R)-BinapRuBr 2 generated in situ. (16) Under these mild conditions, the β-hydroxyester 7 was obtained with 86% yield and the enantiomeric excess was higher than 95%. The enantiomeric excess was determinated by chiral gas chromatography. (17) The diastereoselective amination was carried out with dibenzylazodicarboxylate as electrophilic reagent for the amination step because the conditions of the deprotection of a benzyl carbamate are compatible w...

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Ultrasound-Assisted Cleavage of N-N Bonds in Hydrazines by Raney Nickel

Cited by 54 publications

References 0 publications

Enantioselective Organocatalytic Conjugate Addition of Aldehydes to Vinyl Sulfones and Vinyl Phosphonates as Challenging Michael Acceptors

Enantioselective Organocatalytic Conjugate Addition of Aldehydes to Vinyl Sulfones and Vinyl Phosphonates as Challenging Michael Acceptors

Scandium Triflate in Organic Synthesis

Rapid Asymmetric Synthesis of Highly Functionalized C5 Chiral Synthons. Practical Preparation of trans-3-Hydroxy-D-Proline

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