Aldehydes imidazolidines

The imidazolidine was prepared from an aldehyde with A/,N -dimethyl-1,2-eth-ylenediamine (benzene, heat, 78% yield) and cleaved with Mel (Et20 HjO, 92% yield). Derivatization is chemoselective for aldehydes. The imidazolidine is stable to BuLi and LDA. The diphenylimidazolidine has been prepared analogously and can be cleaved with aqueous HCl. ... 

The chiral bicyclic imidazolidine 74 is deprotonated at the 2 position by s-BuLi and the resulting anion adds to alkyl halides, acid chlorides, chlorofor-mates, phenyl isocyanate, and aldehydes. The use of this compound as a chiral formyl anion equivalent seems to be limited, however, since the diastereoselectiv-ity in the addition to aldehydes is poor and hydrolysis of the products 75 to give aldehydes also produces cyclohexane-1,2-diamine, necessitating isolation of the aldehyde as its 2,4-dinitrophenylhydrazone (96SL1109 98T14255). 

The preparative value of this compound lies in the surprising fact that bis(l,3-diphenylimidazolidinylidenc-2) behaves in many reactions ie.g., with aromatic aldehydes,2,7 and with carbon acids 2 7-fJ) as if it dissociated to form a nucleophilic carbene. The hydrolytic cleavage of these derived imidazolidine derivatives makes possible the preparation of formyl compounds, so that the amino olefin can be considered as a potential carbonyla-tion reagent. In many reactions it is not necessary to isolate... 

A series of imidazolidin-4-ones 117 were prepared from a-amino amides 116 that reacted with aldehydes without solvent at 200 °C imder microwave irradi-... 

In 2002, Braga et al. reported the enantioselective addition of ZnEt2 to various aldehydes performed in the presence of chiral imidazolidine disulfides derived from L-cysteine. In the presence of 5mol% of ligand, the secondary alcohols were isolated in enantioselectivities of up to 91% ee. Aromatic... 

Scheme 3.12 L-Cysteine-derived imidazolidine disulfide ligands for additions of ZnEt2 to aldehydes.

The solvent-free preparation of 1,2,3-trisubstituted imidazolidin-4-ones from aldehydes and N-substituted a-amino acid amides has been reported by Pospisil and Potacek (Scheme 6.202) [365], The general procedure simply involved heating equimolar mixtures of the aldehyde and amine building blocks under open-vessel micro-wave irradiation for 5 min at 200 °C. After cooling to room temperature, the imida-zolidin-4-one products were purified by flash chromatography. 

Aldehydes can also be laterally lithiated if protected as imidazolidines (527) or as imines (528)". With imines, LUMP must be used to prevent nucleophilic addition to C=N (Scheme 207). 

This strategy was further developed so as to prepare the quinolizidine polyol 155 (315), by separating the racemic furoisoxazoline acetals (21,82,293,294) derived from the imidazolidine derivatives, which in turn, were obtained from (15, 25)-diphenylethylenediamine (316) (see Scheme 6.78). Aminal hydrolysis led to aldehyde 153, and this was followed by aldehyde reduction and catalytic hydrogenation (221,313) to give (-l-)-deoxynojirimycin (natural). Its enantiomer was... 

Other chiral azomethine ylide precursors such as 2-(ferf-butyl)-3-imidazolidin-4-one have been tested as chiral controllers in 1,3-dipolar cycloadditions (89). 2-(ferf-Butyl)-3-imidazolidin-4-one reacted with various aldehydes to produce azomethine ylides, which then were subjected to reaction with a series of different electron-deficient alkenes to give the 1,3-dipolar cycloaddition products in moderate diastereoselectivity of up to 60% de. 

Few methods are available to determine enantiomeric purity of aldehydes by NMR spectroscopy of diastereomeric derivatives. The formation of imines. oxazolidines and more recently the advantageously C2-symmetrical imidazolidines with optically pure reagents can be utilized. 

Determination of Enantiomeric Purity of Chiral Aldehydes Using F-NMR Spectroscopy of Their Diastereomeric Imidazolidines... 

Y,A, -Dimethyl-l,2-bis[3-(trifluoromethyl)phenyl]-1,2-diaminocthanc, prepared in two steps from 3-trifluoromethylbenzaldehyde65, can be easily resolved with tartaric acid and reacted with aldehydes at room temperature to give imidazolidines. 

Table 14. F Chemical Shift (C6D6) of the Two CFj-Signals of Diastereomeric Imidazolidines Derived from Selected Aldehydes (Data Adapted from ref 65)...

Werden Aldehyde mit Amin-Hydrochloriden, lsonitrilen und Kaliumcyanat in Methanol/Was-ser-Gemischen umgesetzt, so werden 4-Imino-2-oxo-imidazolidine (4-Amino-2-hydr-oxy-imidazole) erhalten42d ... 

The formylation of phenols with the electron-rich olefin to give imidazolidin-2-yl-phenols is very selective and avoids mixtures of o- and p-isomers which are frequently obtained by methods commonly employed for the synthesis of phenolaldehydes. Para substitution of the cyclic aminal group in the phenol is preferred. If the p-position is blocked or sterically hindered, the reaction proceeds via the ortho- aminals to salicylaldehydes. Incorporation of more than one aldehyde group in the benzene nucleus is often achieved with hydroxy- and aminophenols. 

The protection of formaldehyde or other aldehydes as acyclic dithioacetals, sulfanylethers, sulfonylethers, thiosulfoxides, diselenoacetals, aminothioacetals and aminals, as well as cyclic dithioacetals, dioxolanes, oxazolidines and imidazolidines, allows the preparation of different type of protected acyllithium derivatives IV-XI by deprotonation (see... 

Imidazolidines are not particularly well known they may be considered as aldehyde-ammonias, and can be converted into the aromatic imidazoles only with extreme difficulty if at all. Quinones and azo compounds dehydrogenate 1,3-diphenylimidazolidine, but only as far as the imidazolinium ion [Pg.427]

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