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Stabilized Metalated Aziridines

A tert-butyl ester serves as an efficient organyl-stabilizing group for a lithiated aziridine when the N-protecting group is a chelating moiety. Deprotonation/elec- [Pg.173]

In direct contrast with the chemistry of epoxides [81], trapping of the intermediate lithiated aziridine was possible with external electrophiles (which would [Pg.176]


Sulfonylaziridine 243 was halogenated in carbon tetrahalides in the presence of KOH as base [86] (Scheme 5.61). Although other examples of electrophile trapping of sulfonyl- and phosphonyl-stabilized metalated aziridines exist, the reactions were not stereoselective [87]. [Pg.174]

Desilylation of a,P-aziridinylsilanes is a route to nonstabilized metalated aziridines. Treatment of 254 with CsF in the presence of PhCHO furnished substituted aziridine 255 in good yield (Scheme 5.65). Interestingly, the isomeric aziridine 256 gave azirine 257 on treatment with CsF, presumably via a phenyl-stabilized metalated aziridine [91]. [Pg.175]

As well as for metalated epoxides, the trifluoromethyl moiety also proved an effective organyl-stabilizing group for metalated aziridines. Lithiated aziridine 241 reacted stereoselectively with carbonyl-containing electrophiles, and phenyl disulfide and chlorotrimethylsilane were also trapped in good yield (Scheme 5.60) [70b, 85],... [Pg.174]

Florio et al. have employed heteroaromatic rings as organyl-stabilizing groups for metalated aziridines as well as for metalated epoxides. Regioselective deprotonation of aziridine 246 with n-BuLi, followed by addition of Mel, gave aziridine 247 (Scheme 5.62) [88]. [Pg.174]

Since the mid-1990s, synthetic attention has been directed more towards the use of metal-stabilized nitrenes as synthetic effectors of alkene aziridination. In 1969 it was reported that Cu(i) salts were capable of mediating alkene aziridination when treated with tosyl azide, but the method was limited in scope and was not adopted as a general method for the synthesis of aziridines [12]. Metaloporphyrins [13] were shown to be catalysts for the aziridination of alkenes in the presence of the nitrene precursor N-tosyliminophenyliodinane [14] in the early 1980s, but the reaction did... [Pg.122]

Metalated Epoxides and Aziridines in Synthesis 5.2.4.2 Silyl-stabilized Lithiated Epoxides... [Pg.164]

Silver has three synthetically useful oxidation states Ag(I), Ag(II), and Ag(III).16 Free Ag(III) is very unstable, and most currently known Ag(III) complexes are stablized with electron-donating and/or sterically demanding ligands.17 It is known that Ag(I) can be oxidized to Ag(II) with strong oxidants such as persulfates. Nitrogen-based ligands such as pyridines are commonly used to stabilize high-valence metal ions.18 In 2003, He and coworkers utilized a pyridine-supported silver catalyst and reported the first silver-catalyzed aziridination of olefins.19... [Pg.169]

Depending on the mode of generation, a carbene may be initially formed in either the singlet or triplet state, irrespective of its stability. Common methods used for the generation of carbenes include photolytic, thermal, or metal catalyzed decomposition of diazocompounds, elimination of halogenfrom gem-dihalides, elimination of Hx from CHX3, decomposition of ketenes, thermolysis of a-halo-mercury compounds and cycloelimination of shelf stable substrates such as cyclopropanes, epoxides, aziridines and diazirines. [Pg.93]

This chapter focuses the attention on the reactions of nonstabilized carbanionic compounds such as alkyl, vinyl, aryl, alkynyl metals, etc., and the chemistry of the stabilized system, i.e. allylic, propargylic or oxaallylic carbanions is presented in Volume 2 of this series. Electrophiles with C=X bonite which are discussed include aldehydes, ketones, epoxides, aziridines, acetals, orthoesters and imines, all of which turn into highly reactive electrophiles in the presence of Lewis acids. [Pg.326]

III.B.2), complexes with manganese, chromium, as well as second- and third-row transition metal ions (e.g., ruthenium) oxidation reactions with dioxygen alone or with other peroxides (e.g., ferf-butyl-peroxide) the stabilization and spectroscopic characterization of mononuclear superoxo, peroxo, and oxo complexes other catalytic processes (e.g., the iron-catalyzed aziridination), enantioselective reactions with chiral bispidine ligands and the iron oxidation chemistry continues to produce novel and exciting results. [Pg.690]

The formation of stabilized imino-iodanes as nitrene precursors has been exploited widely in aziridination of alkenes. Traditionally, isolated iminoiodanes have been the preferred route toward transition metal mediated or catalyzed aziridination or C-H amination chemistry [33]. Despite the great success in this field, some reports have become available on the corresponding transition metal-free variants. For example, Padwa reported an iodine(lll)-mediated aziridination of some carbamates 43 from allylic alcohols that in situ formed the corresponding imino-iodanes. Unexpectedly, these compounds underwent direct aziridination to the putative tricyclic compound 44, which was subsequently opened by addition of suitable nucleophiles to arrive at the 1,2-difunctionalized product 45 in a completely stereoselective manner (Scheme 11) [34]. This transformation constituted the proof of concept that iodine(lll)-mediated aziridination does not necessarily require metal promoters. [Pg.114]

Katsuki described the utility of chiral bisoxazolines (chiral ligand A) and 1,2-diimine ligands (chiral ligand B) in enantioselective alkylative cyclization of a range of alkenes using metal-stabilized nitrenes originated from A-tosyliminophenyliodinane and CuOTf to produce chiral aziridines 166 and 168 (Scheme 40.32). [Pg.1227]


See other pages where Stabilized Metalated Aziridines is mentioned: [Pg.173]    [Pg.173]    [Pg.486]    [Pg.6]    [Pg.6]    [Pg.565]    [Pg.15]    [Pg.44]    [Pg.121]    [Pg.130]    [Pg.441]    [Pg.28]    [Pg.114]    [Pg.321]    [Pg.228]    [Pg.584]    [Pg.959]    [Pg.962]    [Pg.454]    [Pg.833]    [Pg.69]    [Pg.33]    [Pg.343]    [Pg.102]    [Pg.338]    [Pg.450]    [Pg.148]   


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Aziridines stability

Metallic stabilizers

Metals stabilization

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