Ketones imidazolidines

The BS2 catalyst was more selective toward the formation of the dialkylated product than the Pd catalysts tested. The activity of BS2 for DAE-MIBK reaction was slower than that with acetone due to steric effects posed by the larger ketone. Here again, the imine tends to rapidly cychze to form imidazolidines or pyrimidines. Figure 17.2 shows the stepwise formation of various side products observed during the reductive alkylation of DAE with acetone. 

The current work indicates that sulfided platinum catalysts are, in general, more active and selective than Pt, Pd, or sulfided Pd catalysts for reductive alkylation of primary amines with ketones. The choice of the catalyst preparation parameters, especially the support, plays a major role in determining the performance of the catalyst. Diamines, especially of lower molecular weight, tend to react with ketones even at room temperature to form heterocycles such as imidazolidine, diazepanes, and pyrimidines. Hence, a continuous reactor configuration that minimizes the contact between the amine and the ketone, along with a highly active catalyst is desired to obtain the dialkylated product. In general, sulfided Pt appears to be more suited for the reductive alkylation of ethylenediamine while unsulfided Pd or Pt may also be used if 1,3-diaminopropane is the amine. 

Nitrone cycloaddition reactions with alkynes have been widely used for the synthesis of imidazolidine nitroxides (736) and (737), containing chelating enam-ino ketone groups (821). Different heterocyclic systems were obtained, such as 3-(2-oxygenated alkyl)piperazin-2-ones (738) (822), also compounds containing the isoxazolo[3,2-i]indole ring system (739) (823) and a new class of ene-hydroxylamino ketones- (l )-2-( 1-hydroxy-4,4,5,5-tetraalkylimidazolidin-2-ylidene)ethanones (740) (824) (Fig. 2.46). 

Rhodium(I) and ruthenium(II) complexes containing NHCs have been applied in hydrosilylation reactions with alkenes, alkynes, and ketones. Rhodium(I) complexes with imidazolidin-2-ylidene ligands such as [RhCl( j -cod)(NHC)], [RhCl(PPh3)2(NHC)], and [RhCl(CO)(PPh3)(NHC)] have been reported to lead to highly selective anti-Markovnikov addition of silanes to terminal olefins [Eq. 

Table 14 presents the chemical shifts of l9F-signal pairs of selected diastereomeric imidazolidines. The advantages of the above method can be summarized as follows high chemose-lectivity-ketones do not react C2 symmetry means a diastereomeric control excess reagent can be easily removed generally, an excellent separation of H-, l3C- and, 5F-NMR signals of the diastereomers is observed. 

Keywords iV-acyl imidate, imidazolidine ketone aminal, microwave irradiation, 2,3-dihydro imidazol[ 1,2-c]pyrimidine... 

Literature reports on iron-catalyzed alkene diamination are scarce. Li et al. described the synthesis of imidazolidine derivatives with an FeCl3-PPh3 complex. As substrates, a, 3-unsaturated ketones and a,P-unsaturated esters were used. The products were obtained in good to high yields and with excellent stereoselectivity (Scheme 3.18). Interestingly, the iron catalyst system worked much better than a previously described rhodium catalyst. Furthermore, the iron catalyst is inexpensive and easier to handle because it is less hygroscopic [104],... 

There have been investigations of the reaction of cyclic thioureas with unsaturated carbonyls. For example, interactions involving imidazolidine-2-thione 64 (n = 1) or tetrahydropyrimidine-2-thione 64 (n = 2) with ketones 65 (k = 1-3) in the presence of the catalyst boron trifluoroetherate yielded only one stereoisomer 66 according to Perjesi et al. [70] (Scheme 3.20). 

Inspired by the proline-catalyzed Robinson annulation pioneered by Wiechert, Hajos, Parrish and coworkers [39], they were able to construct cyclohexanones of type 2-107 with up to four stereogenic centers with excellent enantio- and di-astereoselectivity from unsaturated ketones 2-104 and acyclic ( i-ketoesters 2-105 in the presence of 10 mol% phenylalanine-derived imidazolidine catalyst 2-106. The final products can easily be converted into useful cyclohexanediols, as well as y- and E-lactones. 

Hydrazin 2,2-Dimethyl-l-(2-ethoxy-carbonyl-1 -ethyl-ethenyl)- E15/1, 759 (Keton + R2N-NH2) Imidazolidin 5,5-Dimethyl-l-... 

DIPHENYL-2,4-IMIDAZOLIDINE-DIONE, MONOSODIUM SALT see DNUOOO DIPHENYL KETONE see BCS250 DIPHEN"YLMERCURY see DWX)800 DIPHENYLMETHAN-4,4 -DIISOCYANAT(GERMAN ) see MJP400... 

Reductive cleavage of imidazolidines 641 was implicated in the one-pot synthesis of N,N,N -trisubstituted ethylenediamines 643 from V,V -disubstituted ethylene diamines and an aldehyde R CHO. Presumably the intermediate iminium ion 642 is reduced by NaBH4 (Scheme 154) <2003SC3193>. Naphthalene-catalyzed lithiation of l,3-dimethyl-2-phenylimidazoline 644 leads to benzylic C-N bond cleavage. The intermediate dianion can be trapped with electrophiles (HjO, alkyl halides, ketones, and aldehydes) to afford diamines 645 <2005T3177>. 

Oxa-thiolanes and -thianes combine the properties of oxygen and sulfur acetals. Thus they can be cleaved with mercury salts and are also more labile towards acids than the sulfur analogs. In addition, oxazolidines, imidazolidines and thiazolidines can be used for the protection of aldehydes and ketones however, they have not found a broader use in protecting group chemistry. 

The reaction of dichlorocarbene with ketones and diamines results in near quantitative formation of a mixture piperazinones 584 and 585 (80JOC754). As shown in Section III,C,2, piperazine 78 [R = H, R + R = (CH2)s], the minor product of the Rh2(OAc)4-catalyzed decomposition of diazo ester 73, is the result of the dimerization of the intermediate ylide 76 (84JOC113). Tetrahydropyrazines were synthesized through ring expansion of imidazolidines. Thermolysis or photolysis of diazo compounds... 

In order to find a simple preparation of imidazolidine-2,4-dithiones (CLIX), Bucherer and Lieb 48) in 1934 tried to react aldehydes and ketones with sodium cyanide and carbon disulfide. However, they did... 

In a analogous way, Leu-enkephalin and Met-enkepha-lin were rendered resistant to aminopeptidases by condensation with various aldehydes and ketones to form 4-imidazolidine derivatives (Figure 41.9). 

Therefore, it is possible to obtain compounds with four different substituents at the 2- and 5-positions of the 4-oxoimidazoli-dine ring by reacting the appropriate carbonyl compound with an alpha aminonitrile formed in a Strecker reaction from a selected ketone. The oxidation of these imidazolidines by hydrogen peroxide in the presence of catalytic amounts of sodium tungstate in acetic acid gave new stable nitroxyl radicals (12) shown in Chart 4. 

Novel dinitroxide derivatives of ketones, of type (19), have been obtained from the corresponding imidazolidines (20) and offer prospects as spin labels. ... 

Reaction of disecondary amines and carbonyl compounds affords cyclic aminals if the amino groups are in suitable positions relative to one another (1,2-, 1,3-, or 1,4-). For example, 1,3-diamines condense readily with aldehydes or ketones to give hexahydropyrimidine derivatives,966 967 and disecpndary ethylenediamine derivatives give imidazolidines.968... 

Table XVll.A-4 lists 321 componnds, of which 116 are pyrroles, seventy-nine are pyrrolidines, and twenty-eight are pyr-rolines. There are sixteen pyrazoles listed in Table XVII.A-4. Sixty-two imidazoles, ten imidazolidines, and three imidazolines have been identified in tobacco and tobacco smoke. Five componnds with a 1,2,4-triazole ring have been identified in tobacco. Two compounds with a 1,2,3-triazole ring (as benzotriazoles) have been identified in tobacco and tobacco smoke. The componnds in Table XVII.A-4 exhibit a great deal of fnnctionality. Although each contains a five-membered A-containing ring, some are alcohols, ketones, sugar-amines, acids, esters, and imides. Of the 321 compounds listed in Table XVII.A-4, 256 are found in tobacco smoke, 117 are found in tobacco, and 52 are present in both tobacco and tobacco smoke.

Many derivatives of 1,2- and 1,3-dithiols have been used as protecting groups, but those discussed are the most common. Greene and Wuts discuss other methods for protection of ketones and aldehydes, including cyanohydrins, hydrazones, oximes, oxazolidines, and imidazolidines. 9 Most of these are rather specialized and will not be discussed in this general presentation. 

Imidazo[2,l-h]thiazoles [C3NS-C3N2]. Further examples of the reaction between 2-amino-thiazoles (or -thiazolines) and a-bromo-ketones to give imi-dazo[2,l-6]thiazoles (126) have been reported this ring system has also been obtained from imidazolidine-2-thione and a-bromo-ketones, or pro-pargyl bromide, and from l-(2-methoxyethyl)-4-phenylimidazolidin-2-one... 

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