Bis-imines

Bell and Hall have incorporated an organometallic unit into a crown by using the ferrocenyl unit as part of the ring or as a third strand. The unit is incorporated either as the 1,1 -diformylferrocene or the corresponding acid. In the former case, the bis-imine is prepared and reduced to give the saturated crown (see structure 24). In the latter case, the acid is converted into its corresponding chloride and thence into the diamide by reaction with a diamine. Diborane reduction affords the saturated amino-crown. Structure 24 could be prepared by either of these methods but the dialdehyde approach was reported to be poor compared to the amide approach which afforded the product in ca. 60% yield . 

Petrow described the formation of 3-iminoketones from 3-keto-aldehydes and aniline. Cyclization in the presence of aniline hydrochloride and ZnCh smoothly provides the desired quinoline 26. Bis-imine 24 is the proposed intermediate that undergoes cyclization. The aldimine is more reactive than the ketimine toward cyclization thus, cyclization on the aldimine occurs. When the bis-imine is not formed, partial aniline migration can occur which results in mixtures of cyclized products. 

We have previously discussed that keto-aldehydes react with anilines first at the aldehyde carbon to form the aldimine. Subsequent condensation with another aniline formed a bis-imine or enamino-imine. The aniline of the ketimine normally cyclizes on the aldimine (24 —> 26). Conversely, cyclization of the aldimine could be forced with minimal aniline migration to the ketimine using PPA (30 —> 31). The use of unsymmetrical ketones has not been thoroughly explored a few examples are cited below. One-pot enamine formation and cyclization occurred when aniline 48 was reacted with dione 49 in the presence of catalytic p-TsOH and heat. Imine formation occurred at the less-hindered ketone, and cyclization with attack on the reactive carbonyl was preferred. ... 

Molecular and crystal structures of the macroheterocycle 102 were studied by X-ray [96JCS(D)1203]. As for bis-imines of di(o-formylphenyl) telluride 106, [89MI1 91JOM(402)331] only one of two potentially possible intramolecular coordination N Te bonds exists in a molecule of the macrocycle 102, which, in... 

It is likely that initially the open-chain adducts 353 and 354 are formed by the addition of an amino group either to the carbonyl function or to the triple bond, whereupon these intermediates close up to the azepines 355 and their bis-imine tautomers 356. In the H NMR spectra, the methylene protons of 356 are at 2.85-2.97 ppm, whereas the methyl protons are fixed at 2.20-2.27 ppm. The IR spectra show absorption bands corresponding to the aromatic ring (1600 cm ) and to the diazepine cycle C=N double bonds (1580 cm ). However, there are no bands of... 

Evans et al. reported that the bis(imine)-copper (II) complex 25, prepared from chiral bis(imine) ligand and Cu(OTf)2, is also an effective chiral Lewis acid catalyst [34] (Scheme 1.44, Table 1.18). By tuning the aryl imine moiety, the bis(2,6-dichlor-ophenylimine) derivative was found to be suitable. Although the endojexo selectivity for 3-alkenoyloxazolidinones is low, significant improvement is achieved with the thiazolidine-2-thione analogs, for which both dienophile reactivity and endojexo selectivity are enhanced. 

Intramolecular coupling of the easily prepared 12-membered bis(imine) 1 can be used to synthesize the highly annulated 1,4-diazocine 2.12... 

Bis-imine werden im alkalischen Medium ebenfalls nur bis zur Amino-imin- bzw. En-diamin-Stufe reduziert7 ... 

Das cyclische Bis-Imin I kann unter 1,4-Reduktion zum 2,3-Diphenyl- ,4,5,6-tetrahy-dro-pyrazin hydriert werden2 ... 

These complexes can be isolated in some cases in others they are generated in situ from appropriate precursors, of which diazo compounds are among the most important. These compounds, including CH2N2 and other diazoalkanes, react with metals or metal salts (copper, palladium, and rhodium are most commonly used) to give the carbene complexes that add CRR to double bonds. Ethyl a-diazoacetate reacts with styrene in the presence of bis(ferrocenyl) bis(imine), for example, to give ethyl 2-phenylcyclopropane-l-carboxylate. Optically active complexes have... 

Zhang et al. [49] prepared a chiral ruthenium complex coordinated by a pyridine-bis(imine) ligand (structure 43 in Scheme 21). 

Symmetrical N, N -disubstituted imidazolium salts are usually obtained by addition of paraformaldehyde on a bis-imine of glyoxal under acidic conditions. A one-pot procedure has been developed. Several enantiomerically pure amines were used to prepare the corresponding symmetrical salts 6 (Scheme 4) [12,13]. 

The silylated bis-imine of benzil 1508 reacts with benzaldehyde in benzene, at 90 °C, in the presence of catalytic amounts of AICI3, to afford 2,4,6-triphenylimida-zole 521 in 83% yield [49] (Scheme 9.30). 

Dirheniumheptoxide 2154 is converted by TCS 14, in the presence of 2,2 -dipyri-dine, into the dipyridine complex 2160 [77]. Free ReCls, NbCls, and WCI5 react with HMDSO 7 and 2,2 -bipyridine to form bipyridine oxochloride complexes 2161 and TCS 14, with reversal of the hitherto described reactions of metal oxides with TCS 14. The analogous Mo complex 2162 undergoes silylahon-amination by N-trimethylsilyl-tert-butylamine 2163 to give the bis-imine complex 2164 and HMDSO 7 [77] (Scheme 13.22). 

Highly c/s-selectivity and low molecular weight distribution polymerization of l -butadiene with cobalt(II) pyridyl bis(imine) complexes in the presence of ethylaluminum sesquischloride effect of methyl position in the ligand... 

Table 1. Solution polymerization results for butadiene usir cobalt(II) pyridyl bis(imine) complexes. Polymerization conditions [l,3-butadiaie]= 1 mol/L [Cal.] = 2.00 x 10" mol/L ...

There is no doubt that electrochemically xanthine is initially oxidized to uric acid, which is then further oxidized to a bis-imine that undergoes hydrolysis giving ultimately alloxan, allantoin and urea. There is no single enzyme in man that will bring about such a fragmentation of xanthine. However, there are organisms that possess a combination of enzymes, e.g., xanthine oxidase and certain peroxidases, that under conditions comparable to those employed in the... 

Gawronski et al.21 have used NMR spectroscopy, especially NOE experiments in order to assign conformation of the chiral calixsalen-type macrocycles, products from the [3 + 3] cyclocondensation of the trans-1,2-diaminocyclohexane with hydroxydialdehydes. It was shown that the macrocycles had C3-symmetrical structure and s-syn conformation of imine C—H/cyclohexane axial C—H bond systems and s-trans conformation of the bis-imine unit. 

It should be pointed out that a structurally related bis(imine-phenoxy)Ti complex 54 (Fig. 32) having a C6F5 on the imine-N with MAO activation does not initiate living ethylene polymerization. Interestingly, DFT calculations suggested that there is virtually no interaction between the ortho-F and the 3-H (ortho-F/ 3-H distance 3.66 A) (Fig. 33) [21]. 

Chelating bis(imine) ligands such asA-alkyl(2-pyridyl)methanimine (AlkPMI) have also been successfully utilized in copper-mediated ATRP [74,75,76,77,78]. In... 

Beyond palladium, it has recently been shown that isoelectronic metal complexes based on nickel and platinum are active catalysts for diyne reductive cyclization. While the stoichiometric reaction of nickel(O) complexes with non-conjugated diynes represents a robust area of research,8 only one example of nickel-catalyzed diyne reductive cyclization, which involves the hydrosilylative cyclization of 1,7-diynes to afford 1,2-dialkylidenecyclohexanes appears in the literature.7 The reductive cyclization of unsubstituted 1,7-diyne 53a illustrates the ability of this catalyst system to deliver cyclic Z-vinylsilanes in good yield with excellent control of alkene geometry. Cationic platinum catalysts, generated in situ from (phen)Pt(Me)2 and B(C6F5)3, are also excellent catalysts for highly Z-selective reductive cyclization of 1,6-diynes, as demonstrated by the cyclization of 1,6-diyne 54a.72 The related platinum bis(imine) complex [PhN=C(Me)C(Me)N=Ph]2Pt(Me)2 also catalyzes diyne hydrosilylation-cyclization (Scheme 35).72a... 

In 1991, Elsevier reported other nitrogen ligand-containing complexes as active hydrogenating catalysts. Palladium(O) complexes containing the Ar-bian bis-imine... 

Abstract Brookhart and coworkers have recently developed Ni(II) and Pd(II) bis-imine... 

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