Imines trifluoromethanesulfonate

Symmetric triblock copolymers of the ABA type, where B was PTHF and A poly(2-methyl-2-oxazoline), PMeOx, were prepared by cationic polymerization with trifluoromethanesulfonic anhydride as a difunctional initiator [58]. Subsequent hydrolysis of the PMeOx blocks with HC1 in a methanol/ water mixture resulted in the formation of the corresponding polyethylen-imine blocks (Scheme 20). Samples with relatively low molecular weight distributions were obtained. 

Imines of acyclic and C10- to C15-membered carbocyclic ketones are prepared under the conditions described for cyclohexanone imines using trifluoromethanesulfonic acid or trifluoroacetic acid as additional catalyst. The reaction often takes several days in refluxing benzene or toluene9. 

Kitazume and Zulfiqar have investigated the aza-Diels-Alder reaction in 1,8-diazabicyclo[5,4,0]-7-undecenium trifluoromethanesulfonate [EtDBU][OTf] [184] (Fig. 5.2-5). This reaction involved the scandium(iii) trifluoromethanesulfonate catalyzed reaction of an imine (usually generated in situ from an aldehyde and an amine) with a diene. An example of this reaction is given in Scheme 5.2-74. The yields in this reaction were high (80-99%) and it was found that the ionic liquid could be recycled and reused. 

The use of a scandium trifluoromethanesulfonate catalyst has also been reported for aza-Diels-Alder reactions. The reaction of benzaldehyde and amine 104 in [emim][OTf] as the ionic liquid led to the in situ formation of the corresponding imine. Cycloaddition of this imine with Danishefsky s diene gave the A -aryl-6-phenyl-5,6-dihydro-4-pyridone 105 in a quantitative yield (Scheme 44). 

Asymmetric Aziridination of Alkenes. The copper-catalyzed aziridination reaction can be rendered enantioselective by the addition of chiral ligands. The first example of an enantioselective aziridination of an alkene employed the bis(oxazoline) ligand (4) (R = f-Bu) and copper(I) trifluoromethanesulfonate as the metal catalyst (eq 14). This catalyst system affords the aziridine in 97% yield and 61% ee. Other reports have appeared subsequently regarding the extended scope of this reaction. " Important contributions to this area include the copper/bis-(oxazoline)-catalyzed aziridination of aryl acrylate esters (eq 15) and the copper/bis(imine)-catalyzed aziridination of cyclic cis-alkenes with the bis(imine) ligand (5) (eqs 16 and 17). ... 

In the presence of a diphosphonium salt (7 mol%), trimethylsilyl trifluoromethanesulfonate (10 mol %), or iron(in) nitrate-KlO montmorillonite clay, the reagent adds to imines or Al-tosyliminiumions to give the corresponding amino esters in good yield. 

Aldol Reactions Addition to Aldehydes and Imines. Since its discovery, the Mukaiyama aldol reaction. has attracted considerable attention and several improvements in reaction conditions have heen reported. Most useful catalysts for this reaction appear to he recently reported lanthanide triflates (eq 5), bis(cyclopentadienyl)titanium bis(trifluoromethanesulfonate), or Cp2Zr(OTf)2 THF. The metallocene salt also catalyzes additions to ketones (eq 6). This reaction can also be carried out under essentially neutral conditions by warming (70 °C) a stoichiometric mixture of the aldehyde and the KSA in acetonitrile (eq 7). When an optically active aldehyde is used, a slightly better stereochemical control is noticed under catalysis of zinc iodide. ... 

The isolation of the non-cyclic amino(aryl)carbenes and amino(alk-yl)carbenes demonstrated that singlet carbene centres can be sufficiently stabilized by only one a-nitrogen atom. In 2005, Bertrand and co-workers succeeded in preparing the first cyclic alkyl(amino)carbenes (CAACs Scheme 1.15). The precursor for CAAC 108 was obtained from an imine by deprotonation with LDA (LDA = lithium diisopropylamide) and subsequent reaction with 1,2-epoxy-2-methylpropane to give 106, which was converted into cyclic aldiminium salt 107 by reaction with trifluoromethanesulfonic acid... 

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