Imidazolidines, oxazolidines from

For the first time, chiral 1,2-aminoalcohols (or 1,2-diamines) have been used as organocatalysts of a domino Michael-aldol, giving yields/dc/cc up to 91/94/93% in the preparation of a cyclohexanone from an enone and a )8-ketoester. The catalysts (107, X = 0 or NMe) may act as such on their own or when, for example, benzoic acid is used as co-catalyst. However co-catalysis by glycolic acid (0=CH-C02H) may actually involve an imidazolidine/oxazolidine (108). " ... 

Cyclocarbonylation. Oxazolidin-2-ones and imidazolidin-2-ones are formed from 2-amino alcohols and 1,2-diamines in the DMAP-catalyzed reaction with (Boc) 0. 

The three 1,3-azoles, imidazole, thiazole and oxazole, are aU very stable compounds that do not autoxidise. Oxazole and thiazole are water-miscible liquids with pyridine-like odours. Imidazole, which is a solid at room temperature, and 1-methylimidazole are also water soluble, but are odourless. They boil at much higher temperatures (256 °C and 199 °C) than oxazole (69 °C) and thiazole (117 °C) this can be attributed to stronger dipolar association resulting from the very marked permanent charge separation in imidazoles (the dipole moment of imidazole is 5.6 D cf. oxazole, 1.4 D thiazole, 1.6 D) and for imidazole itself, in addition, extensive intermolecular hydrogen bonding. The dihydro- and tetrahydro-1,3-azoles are named imidazoline/imidazolidine, thiazoline/thiazolidine and oxazoline/oxazolidine. 

Synthesis of Heterocycles. Novel synthesis of 1,3-dioxolanes was suggested, which starts with the formation of an intermediate carbonyl ylide from dimethyl diazomalonate and a carbonyl compound (aldehyde or quinone) in the presence of catalytic amounts of Rh. Once formed, the ylide undergoes dipolar [3 + 2] cycloaddition with another equivalent of carbonyl compound to furnish a five-membered heterocycle (eqs 25 and 26). Employment of aldimines in this reaction allowed for preparation of 1,3-imidazolidines (eq 27) and 1,3-oxazolidines (eq 28). ... 

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