Aziridine 1-alkyl-2-aryl-substituted

Of course, the cleavage reactions of both 2-aryl- and 2-alkyl aziridines are stereoselective because only the trans-diastereomers of the corresponding regioisomers 1 and 2 are formed. In other words, 2-aryl substituted aziridines showed opposite regioselectivity to 2-alkyl aziridines. With bicyclic aziridines, exclusive formation of the trans diastereomer is observed in the case of symmetric bicyclic aziridines. Unsymmetrical aziridines such as styrene, octene, and undecene aziridines produce a minor amount of the other regioisomer. 

A very efficient catalytic system has been developed by He and coworkers using, under solvent-free conditions, quaternary ammonium bromide-functionalized polyethylene glycol (0.25 mol% 373 K, 8MPa, 5-20min) [68d]. The catalyst worked well for a variety of l-alkyl-2-aryl-substituted aziridines, and could be easily recovered by centrifugation and reused, without any significant loss of catalytic activity and selectivity. 

The fixation of C02 into a three-membered ring has also been promoted, under relatively severe conditions, by other catalytic systems such as tetrapheny-lantimony halides (333 K, 5 MPa) [68e] or the p-methoxyphenol/DMAP system (DMAP = 4,6-(dimethylamino)pyridine 393 K, 3.6MPa, 48h) [68f] or, under much milder conditions, by alkali [68g-k] or tetralkylammonium halides [68j], or by (Salen)Cr(III)(DMAP) [681]. It is worth noting that, with 2-alkyl or 2-aryl substituted aziridines, alkali or tetralkylammonium halides catalyze the formation of the 4-substituted regioisomer as the main or unique product, whereas the chromium(III) catalyst promoted the preferential conversion to the 5-subshtuted regioisomer with high selectivity and yield. 

Jacobsen reported in 1990 that Mnm complexes of chiral salen ligands (41) were the most efficient catalysts available for the enantioselective epoxidation of alkyl- and aryl-substituted olefins.118 This stimulated a rapid development in the chemistry and applications of chiral SB complexes, which offer promising catalytic applications to several organic reactions, such as enantioselective cyclopropanation of styrenes, asymmetric aziridination of olefins, asymmetric Diels-Alder cycloaddition, and enantioselective ring opening of epoxides.4,119... 

The carbonylation of several classes of aziridines have been reported. In general, the carbonylation of aziridines containing alkyl or benzyl substituents on the two carbon atoms occurs to insert the CO into the C-N bond containing the less-substituted carbon. Equation 17.53 shows a series of these reactions catalyzed by Co2(CO)g. In contrast, the carbonylation of aziridines containing aryl groups on one of the two carbons occurs at the benzylic position. Examples of these reactions are shown in Equation 17.54. Carbonylation of these phenyl-substituted aziridines catalyzed by [Rh(CO)2Cl]j has also been reported by Alper, and a representative example is shown in Equation 17,55. ... 

Aryl alkyl ketoximes also react with aryl or alkyl Grignard reagents to give substituted ethylenimines [44, 45]. Additional methods for the synthesis of ethylenimines (aziridines) is found in Dermer and Ham [lb]. 

Reaction with Carbon Nucleophiles. Unactivated aziridines react with the lithium salts of malonates or p-keto esters in the presence of lithium salts to yield 3-substituted pyrrolidinones (56—59), where R = alkyl and aryl, and R = alkoxyl, alkyl, and aryl. 

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