Imines, reaction with

Because imine has a basic nitrogen atom, a Bronsted acid turned out to be effective as the activator of imines. The seminal work of Akiyama and Terada in 2004 paved the way for chiral Bronsted acid catalysis in nucleophilic addition to imines. 

Enantioselective Mannich reactions are widely used for the construchon of optically active (3-amino carbonyl compounds that serve as versatile intermediates for the synthesis of biologically active compounds [7]. 

Rueping et al. reported achiral Br0nsted acid assisted chiral Bronsted acid catalysis in the direct Mannich reaction of acychc ketones. The reaction of N-aryl imines with acetophenone was conducted using a chiral phosphoric acid in the presence of acetic acid as the co-catalyst and the resulting products were obtained in moderate yields [11]. 

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Synthesis and chemistry of substituted l-azabicyclo[1.1.0]butanes 97SL1029. Synthesis of aziridines via stereoselective reactions with imines 99PAC1033. 

Addition of Methyl Sulfoxides Reactions with Imines... 

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

Pyrrolocarbenes produced low yields of /J-lactams in photodriven reactions with imines [52], while o-acylimidatocarbene complexes gave a mixture of compounds with /J-lactams being minor components [53]. 

Another SBU with open metal sites is the tri-p-oxo carboxylate cluster (see Section 4.2.2 and Figure 4.2). The tri-p-oxo Fe " clusters in MIL-100 are able to catalyze Friedel-Crafts benzylation reactions [44]. The tri-p-oxo Cr " clusters of MIL-101 are active for the cyanosilylation of benzaldehyde. This reaction is a popular test reaction in the MOF Hterature as a probe for catalytic activity an example has already been given above for [Cu3(BTC)2] [15]. In fact, the very first demonstration of the catalytic potential of MOFs had aheady been given in 1994 for a two-dimensional Cd bipyridine lattice that catalyzes the cyanosilylation of aldehydes [56]. A continuation of this work in 2004 for reactions with imines showed that the hydrophobic surroundings of the framework enhance the reaction in comparison with homogeneous Cd(pyridine) complexes [57]. The activity of MIL-lOl(Cr) is much higher than that of the Cd lattices, but in subsequent reaction rans the activity decreases [58]. A MOF with two different types of open Mn sites with pores of 7 and 10 A catalyzes the cyanosilylation of aromatic aldehydes and ketones with a remarkable reactant shape selectivity. This MOF also catalyzes the more demanding Mukaiyama-aldol reaction [59]. 

In the first step, catalyst 64c attacks ketene 66 to form a zwitterionic enolate 71, followed by Mannich-type reaction with imine 76 (Fig. 40). A subsequent intramolecular acylation expels the catalyst under formation of the four-membered ring. Utilizing 10 mol% of 64c, N-Ts substituted (3-lactams 77 were prepared from symmetrically as well as unsymmetrically substituted ketenes 66, mainly, but not exclusively, with nonenolizable imines 76 as reaction partners [96]. Diastereos-electivities ranged from 8 1 to 15 1, yields from 76 to 97%, and enantioselectivities from 81 to 94% ee in the case of aliphatic ketenes 66 or 89 to 98% ee for ketenes bearing an aromatic substituent. Applying complexes 65 or the more bulky and less electron-rich 64b, ee values below 5% were obtained. 

Bransted acid-catalyzed reactions with imines... 

Yamamoto and coworkers described a highly enantioselective asymmetric domino 0-nitroso aldol-conjugate addition seqnence using cyclic enones 221 and aromatic nitroso compounds 222 as depicted in Scheme 36 [346]. A related reaction with imines was also reported by Cdrdova and coworkers (Scheme 37) [228]. 

The ionic liquid [bmim][BF ] is known to catalyze the aza-Diels-Alder reaction in the synthesis of pyrano- and furanoquinolines [190]. This reaction was also catalyzed by the enantiopure bis-imidazolinium salt 67 in 67% yield with an endo. exo ratio of 60 40 (Scheme 69) [191]. The product was obtained as a race-mate. In addition the aza-Diels-Alder reaction with imines and Danishefsky s diene was catalyzed by the salt 67 giving racemic product. The salt and its analogues could be easily prepared via the oxidation of the corresponding aminals [192]. Investigation of the influence of the counter anion in achiral C2-substituted imidazolinium salts, which can be also described as 4,5-dihydroimidazolium or saturated imidazolium salts, in the aza-Diels-Alder reaction showed, that the catalytic activity increased, the more lipophilic the counter anion and therefore the more hydrophobic the salt was [193]. 

Beak and coworkers found the (—)-sparteine-complex of iV-Boc-Af-(p-methoxyphe-nyl)benzyllithium 244, obtained from 243 by deprotonation with n-BuLi/(—)-sparteine (11) in toluene, to be configurationally stable (equation 57) . On trapping 244 with different electrophiles, the substitution products 245 are formed with high ee. Efficient addition reactions with imines and aldehydes have also been reported. The p-methoxyphenyl residue is conveniently removed by treatment with cerinm ammoninm nitrate (CAN). 

Similarly, reaction with imines affords alkyl 2-imidazolidinone-4-carboxylates 293 via [2+2] cycloadducts 292. Treatment of the isolated cycloadducts 292 with trifluoroacetic acid (TFA) yields 2,3-diaminocarboxylates 294. ... 

Monosubstituted-5(4//)-oxazolones behave differently upon reaction with imines. Here, 4-methyl-2-phenyl-5(4/7)-oxazolone 196 (Ri = Ph, R2 = Me) reacts with imines derived from 2-furancarboxaldehyde or 2-thiophenecarboxaldehyde to give 3-amino-p-lactams 197. On the other hand, 196 reacts with chlorosul-fonyl isocyanate in a [2 + 2] cycloaddition to give dioxazabicycloheptanones 198 as shown in Scheme 7.60. ... 

Reactions with imines also occur under similar conditions leading to the formation of difluorinated /1-lactams [196,197]. Formally, this reaction corresponds to a [2+ 2]-cycloaddition across an imine there is also an isolated report of a difluoroketene reaction, shown in Eq. (63) [198]. Useful chemistry of a silyl difluoroketene acetal was reported recently Eq. (64) shows the efficient asymmetric reaction between this reactive carbon nucleophile and aldehydes catalysed by chiral Lewis acids [199]. 

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