Copper aldimines

Except for the well-documented conjugate additions of diethylaluminum cyanide,92 triethylaluminum-hydrogen cyanide and Lewis acid-tertiary alkyl isonitriles,93 examples of Lewis acid catalyzed conjugate additions of acyl anion equivalents are scant Notable examples are additions of copper aldimines (233),94, 94b prepared from (232), and silyl ketene acetals (234)940 to a,(3-enones which afford 1,4-ketoal-dehydes (235) and 2,5-diketo esters (236), respectively (Scheme 37). The acetal (234) is considered a glyoxylate ester anion equivalent. 

Aziridines have been synthesized, albeit in low yield, by copper-catalyzed decomposition of ethyl diazoacetate in the presence of an inline 260). It seems that such a carbenoid cyclopropanation reaction has not been realized with other diazo compounds. The recently described preparation of 1,2,3-trisubstituted aziridines by reaction of phenyldiazomethane with N-alkyl aldimines or ketimines in the presence of zinc iodide 261 > most certainly does not proceed through carbenoid intermediates rather, the metal salt serves to activate the imine to nucleophilic attack from the diazo carbon. Replacement of Znl2 by one of the traditional copper catalysts resulted in formation of imidazoline derivatives via an intermediate azomethine ylide261). 

Figure 5 Bidentate Schiff bases with N,N donor set which act as monoanionic ligands (a) all cis, Rj = R3 = H (b) all trims, R2 = R = H (d) a copper(II) complex with a bidentate monoanionic aldimine...

A-Tosyl aldimines, RCH=N-Ts, add regioselectively to the C(2) of pyrroles, to give pyrrole sulfonamides (11), using copper(II) triflate as catalyst.53... 

The synthesis of novel azetidine derivatives remains the subject of intensive study. New procedures for the preparation of this class of compounds include, e.g., rearrangement of /3,7-aziridino-a-amino esters <2007OL4399>, copper-catalyzed multicomponent reactions of terminal alkynes, sulfonyl azides, and carbodiimides <20070L1585>, regioselective addition of 1,3-dicarbonyl dianions to iV-sulfonyl aldimines <2007T4779>, elaboration of a-amino acids <2007TL2471>, palladium-catalyzed iV-arylation of azetidines <2007S243> and... 

Imines may be activated by complexation with Lewis acids, but this also increases the acidity of a-hydrogen atoms. A combination of copper(i) halide and boron trifluoride etherate is a possible solution to the problem [6, 7]. Activation by trimethylsilyl triflate is also effective with aldimines (though not with ketimines) [7, 8]. 

Enantiomeric purities ranging from 20 to 80% have been reported for the acid-promoted asymmetric oxidation of sulfides to sulfoxides by binaphthyl-derived oxaziridines has been described <2007T6232>. A novel amino hydroxylation of olefins has been developed using /ra t-2-phenylsulfonyl-3-phenyloxaziridine 33 <2007JA1866>. The reaction, which is catalyzed by copper(ll) salts, affords good yields of the product. Oxidation of aldimines to oxaziridines using alumina-supported M0O3 catalyst and anhydrous /-butyl hydroperoxide (TBHP) has been described. Yields are excellent. 

Diethanolamine will react with acids, acid anhydrides, acid chlorides, and esters to form amide derivatives, and with propylene carbonate or other cyclic carbonates to give the corresponding carbonates. As a secondary amine, diethanolamine reacts with aldehydes and ketones to yield aldimines and ketimines. Diethanolamine also reacts with copper to form complex salts. Discoloration and precipitation will take place in the presence of salts of heavy metals. 

As a primary amine, monoethanolamine will react with aldehydes and ketones to yield aldimines and ketimines. Additionally, monoethanolamine will react with aluminum, copper, and copper alloys to form complex salts. A violent reaction will occur with acrolein, acrylonitrile, epichlorohy-drin, propiolactone, and vinyl acetate. 

The chelation of copper(II) with the Schiff base obtained from salicylaldehyde and glycine stabilizes the aldimine bond to such an extent that the metal chelate remains undissociated at pH 3, whereas the Schiff base itself is dissociated at this hydrogen ion concentration (76, 155). In this case, the formation of the bicyclic chelate ring system completely counteracts the electron-withdrawing effect of the metal ion. 

Readily available A -r-butanesulfinylimine derivatives of aldehydes react with B2piii2 in the presence of the NHC-copper catalyst (ICy)Cu-O-t-Bu (5 mol%) to give high ratios of diastereomeric a-amino boronate estersJ Benzene is the solvent of choice, as lower yields are observed for the reaction below, run in toluene (69%), THF (50%), or dioxane (62%). Both alkyl and aryl aldimines participate to give dr s >95 5. The utility of this highly diastereoselective process was demonstrated by its application to a synthesis of bortezomib (Velcade), a U.S. Food Drug Administration (FDA)-approved and clinically useful protease inhibitor. ... 

Considerable effort has been made in developing iV-diphenylphosphinoyl (Dpp) aid- and keto-imines as electrophilic partners in copper-catalyzed 1,2-additions (Scheme 1-10). Thioamides and aldimines e.g., 123) in the presence of a soft Lewis acidic Cu(I) salt complexed by 6/5-phosphine 124, together with a hard base in the form of a lithium phenoxide, react to afford products in good-to-excellent ee s. Activation resulting from a likely Cu-S interaction increases the acidity of an a-proton and, hence, more facile deprotonation. With alkyinitriles as nucleophiles generated via an initial decarboxylative process e.g., from 125), a DTBM-SEGPHOS-coordinated copper complex arrives at C-C bond formation in usually >80% ee. 

A-Sulfinyl aldimines undergo Friedel-Crafts reaction with indoles in up to 99% ee, using a copper(II)-bis(oxazoline) catalyst. An organocatalytic asymmetric aza- 0 Friedel-Crafts alkylation of naphthols with A-sulfonylimines has been developed, giving yields and ees up to 99% 0... 

The Au(I)- or Ag(I)-catalysed intermolecular hetero-Diels—Alder cycloaddition of push-pull l,3-dien-5-ynes (76) with aldimines or silylaldimines (77) produced 5,6-dihydropyridin-2-ones (78) with high diastereo- and regio-selectivities (Scheme 24). A copper-catalysed intramolecular aza-Diels—Alder reaction has been used to produce dihydrochromeno[4,3-Mpyrrolo[3,2-/ quinolmes in good yields. The cinchonidine-derived quaternary ammonium catalyst, A-2, 3, 4 -trifluorobenzyl-0-benzylcinchonidinum bromide (79), catalysed the aza-Diels—Alder reactions between... 

---