1.3- Imidazolidines

The electron density induced at the metal center increases in the order C(OR)R < C(NHR)R < C(NHR)2 imidazolidin-2-ylidene imidazolin-2-ylidene. According to these data the difference between diamino-substituted carbenes whether cyclic or acyclic, aromatic or nonaromatic, seems to be quite small. 

The dithiocarbamate fungicides have been popular for agricultural use because of their effectiveness and relatively low toxicities to animals. However, there is concern over their environmental breakdown products, particularly ethylenethiourea (2-imidazolidine thione see Figure 17.5), which is toxic to the thyroid and has been shown to be mutagenic, carcinogenic, and teratogenic in experimental animals. 

In an investigation by Wehner (2), imidazolidine derivatives, (II), were effective as integrin antagonists and used in treating rheumatoid arthritis or allergic diseases. 

Additional 2-imidazolidine derivatives, (I), effective as a1L-adrenoreceptor agonists were prepared by the authors (1) in earlier investigations and used in the treatment of stress incontinence in women. 

Rearrangement of 3-alanine and succinic acid derivatives (100 and 102) gives l-acyl-2-imidazolidin-ones (101) and 3-alanine derivatives (103) respectively (Scheme 22). However, the -methylcarbox-... 

A series of 2-imidazolidin-2-one substituted benzothiazoles 62 are prepared from O-amidinylhydroxylamines 58 with aryl isothiocyanates 59 in moderate yields <05PJC115>. The reaction pathway has been proposed to proceed via iminocarbonyl sulfenamide 61, which undergoes spontaneous sulfurization of the aromatic ring with loss of 1-aminocyclohexanecarbonitrile to furnish benzothiazole 62. 

Chlormelhyl-2-(dimethylamino-methyl)- 31 4-Chlormethyl-2-(imidazolidin-2-yliden-amino)- 59... 

This type of cyclization has been used mainly to prepare imidazo[2,l-fe]thiazoles and imidazo[l,2-6]pyrazoles (Schemes 13 and 14). Base-catalyzed cyclizations of 2-(cyanoimino)thiazolidines (124) afforded imidazo[2,l-6]thiazoles (126) via intermediates (125). Cyclization of (124) only occurs when R is an electron withdrawing group <885261 >. Imidazo[l,2-6]pyrazoles have been prepared from suitably substituted imidazolidine derivatives <80JHC1413>. The imidazolidine (127), prepared in 5 stages from 2-imidazolidine thione, was subjected to a hydrazinolysis reaction initiated by 2,4-dinitrophenylhydrazine to give a mixture of imidazo[l,2-fe]pyrazoles (129) and (130) and the hydra-zone (128). 

Lewis acid catalysed [3 + 2] cycloaddition of A-alkoxycarbonylaziridines and cyanoalkane such as MeCN furnishes 2-imidazolidines [39] (Scheme 3.23). Although ring-fused aziridines are useable as substrates, cii-stereochemistry in the ring juncture is isomerized to frawi-stereochemistry in the bicyclic amidine products. Benzonitrile also serves as a nitrile source. 

Application to chiral A-acylaziridine-2-carboxylate gives the corresponding chiral 2-imidazolidine with the retention of configuration [40] (Scheme 3.24). This implies that the... 

Other nonderivatizing solvents, such as LiCl-DMI (l,3-dimethyl-2-imidazolidin-one) and tetrabutylammonium fluoride trihydrate-Me2SO, have also been... 

Thiuronium salts 76 and 78 were quantitatively obtained when 2-imidazolidine thi-one 74 or 2-mercaptobenzimidazole 77 were ball milled with phenacyl bromide by the procedure reported by Kaupp et al. (Scheme 4.20) [14]. For this reaction, equimolar amounts of reagents were used. Similar reactions in solution, on the other hand, are incomplete and generate corrosive wastes. 

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