Über die Reaktion von Grignard‐Verbindungen mit Schiffschen Basen, I. Mitteil.: Die Bildung von Äthylendiaminderivaten

Thies, Heinrich; Schoenenberger, H.

doi:10.1002/cber.19560890819

Cited by 26 publications

(5 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The poor result obtained with benzylideneaniline as the imine was surprising (Table , entry 5). We can only speculate that the extended π system of the benzylideneaniline may be too good of an electron acceptor, thereby allowing competing reaction pathways, e.g., reductive dimerization, to supersede the desired course of addition. In general, however, the reaction procedure appears to accommodate a variety of substrates and provides access to a number of substituted isoindolones.…”

Section: Resultsmentioning

confidence: 99%

Addition of Transiently-Generated Methyl o-Lithiobenzoate to Imines. An Isoindolone Annulation

1996

View full text Add to dashboard Cite

Addition of phenyllithium to a mixture of an imine, methyl o-iodobenzoate, and BF(3).etherate at -105 degrees C gives good to excellent yields of isoindolones. The transient formation of methyl o-lithiobenzoate is proposed, which is formed by a rapid lithium/iodide exchange reaction of the phenyllithium with methyl o-iodobenzoate in the presence of the imine. The transiently generated anions can then be captured by the BF(3)-activated imines to form the isoindolones in good to high yield. The reactions conditions are sufficiently mild, and selective, to permit functional groups such carbmethoxy and aryl bromide, which could otherwise react with the added PhLi, to be tolerated.

show abstract

Section: Resultsmentioning

confidence: 99%

Addition of Transiently-Generated Methyl o-Lithiobenzoate to Imines. An Isoindolone Annulation

1996

View full text Add to dashboard Cite

show abstract

“…Investigations into a reverse addition procedure for the organometallic additions: Although the potential radical nature of the additions remained unconfirmed, the formation of dimer 32 nonetheless highlighted the propensity of imine substrates in such homo-coupling, perhaps through Mg-chelated, pinacol reduction. [38] It was considered that addition of the imine to the Grignard, rather than Grignard to imine, might counter this problem. Such a reverse addition, by presenting a high Grignard concentration to a low imine concentration rather than vice versa, would likely curtail such dimerization side reactions that are more dramatically dependent on imine concentration.…”

Section: Optimisation Of Organometallic Additionsmentioning

confidence: 99%

Highly Diastereoselective Additions to Polyhydroxylated Pyrrolidine Cyclic Imines: Ready Elaboration of Aza‐Sugar Scaffolds To Create Diverse Carbohydrate‐Processing Enzyme Probes

Chapman

Courtney

Hay

et al. 2003

Chemistry A European J

View full text Add to dashboard Cite

Representative diastereomeric, erythritol and threitol polyhydroxylated pyrrolidine imine scaffolds have been rapidly elaborated to diversely functionalized aza-sugars through highly diastereoselective organometallic (RM) additions (R=Me, Et, allyl, hexenyl, Ph, Bn, pMeO-Bn). The yields for these additions have all been substantially enhanced from previously optimised levels (<58 %) for normal additions using a reverse addition procedure (e.g. R=Ph; 44 % normal mode --> 78 % reverse mode). The high diastereoselectivities (>98 % de for all except R=Me) are consistent with additions that are controlled by the configuration of the C-2 centre adjacent to the azomethine imine carbon and the conformation of the pyrrolidine imine. The high potential of this method was demonstrated by concise syntheses of 1-epi- and 2-epi-desacetylanisomycins. In addition, the late stage addition of hydrophobic substituents, which this imine addition methodology allows, enabled the preparation of novel aza-sugars with enhanced inhibitory potential. This was highlighted by the screening of a representative selection of these "hydrophobically-modified" aza-sugars against a diverse panel of 12 non-mammalian and human carbohydrate-processing enzymes. This identified a novel nanomolar alpha-galactosidase inhibitor (IC(50)=250 nM) and a novel highly selective glucosylceramide synthase inhibitor (IC(50)=52 microM, no alpha-glucosidase inhibition at 1 mM). Furthermore, analysis of the structure-activity relationships of racemic series of inhibitors allowed some validation of Fleet's mirror-image enzyme active site postulate.

show abstract

“…This differs significantly from mutual thermal routes like alkylation with organometallic compounds, 9-11 which is not regioselective and suffers from competing isomerization, 10 deprotonation, 12 and dimerization. 13 In the following we report that semiconductor photocatalysis type B also enables the synthesis of new unsaturated N-phenyl-α-amino acid esters. Furthermore, experimental evidence for the presence of the proton coupled reduction step is presented.…”

Section: Introductionmentioning

confidence: 96%

Semiconductor photocatalysis type B: synthesis of unsaturated α-amino esters from imines and olefins photocatalyzed by silica-supported cadmium sulfide

Hopfner

Weiß

Meißner

et al. 2002

Photochem Photobiol Sci

View full text Add to dashboard Cite

Novel unsaturated N-phenyl-alpha-amino esters were synthesized in isolated yields of 50 to 10% by visible light irradiation of methanolic suspensions of silica-supported cadmium sulfide in the presence of methyl (2Z)-phenyl(phenylimino)acetate and various cyclic olefins. A semiconductor photocatalysis mechanism is proposed for this linear addition reaction. The light-generated electron-hole pair in the oxidative step induces a dissociative electron transfer from the olefin to CdS affording a proton and an allylic radical, whereas in the reductive step an alpha-aminobenzyl radical is formed in a proton coupled reaction. Heterocoupling of these intermediate radicals leads to the corresponding addition products. As the only by-product the hydrogenated imine is obtained in comparable amounts through the subsequent photoreduction of the alpha-aminobenzyl radical. Supporting the catalyst on silica made the reaction three times faster as compared to neat CdS. When the surface OH groups of CdS were removed through alkylation, the reaction between ArCH=NAr (Ar = p-C1C6H4) and cyclopentene was completely inhibited, but occurred again upon replacing the aldimine by its hydrochloride salt. This indicates that the protonated aldimine is involved in the reductive reaction step. Protonation makes this reduction easier by 0.1 V as indicated by the shift of the reduction potential of methyl (2Z)-phenyl(phenylimino)acetate upon addition of glacial acetic acid to the acetonitrile solution.

show abstract

Über die Reaktion von Grignard‐Verbindungen mit Schiffschen Basen, I. Mitteil.: Die Bildung von Äthylendiaminderivaten

Cited by 26 publications

References 10 publications

Addition of Transiently-Generated Methyl o-Lithiobenzoate to Imines. An Isoindolone Annulation

Addition of Transiently-Generated Methyl o-Lithiobenzoate to Imines. An Isoindolone Annulation

Highly Diastereoselective Additions to Polyhydroxylated Pyrrolidine Cyclic Imines: Ready Elaboration of Aza‐Sugar Scaffolds To Create Diverse Carbohydrate‐Processing Enzyme Probes

Semiconductor photocatalysis type B: synthesis of unsaturated α-amino esters from imines and olefins photocatalyzed by silica-supported cadmium sulfide

Contact Info

Product

Resources

About