Cycloaddition of aziridines

Cycloadditions of aziridines to diphenylcyclopropenone lead to 4-oxazolines (36) (70CJC89). A mechanism involving initial addition to the cyclopropenone carbonyl group followed by ring opening and recyclization was suggested. 

Intramolecular and intermolecular 1,3-dipolar cycloadditions of aziridine-2-car-boxylic esters with alkenes and alkynes have been investigated [131, 132]. Upon heating, aziridine-2-carboxylates undergo C-2-C-3 bond cleavage to form azome-... 

The [3 -f 2] cycloaddition of aziridines and dipolarophiles, like dimethyl acetylenedicarboxylate or dimethyl fumarate and maleate, was investigated by Gaebert and Mattay. Via C—C and C—bond cleavage five-membered heterocycles are formed in moderate yields. The different product ratios dependent on the reaction conditions (PET/direct excitation/thermal reaction) gave insights to the reaction details and are summarized in the proposed mechanism (Scheme 52) [84],... 

Lewis acid-promoted [3+2] cycloadditions of aziridines and epoxides proceeding via carbon-carbon bond cleavage of three-membered ring heterocycles are demonstrated for the first time. This proposal details plans for extending these initial results into a general synthetic method for the enantioselective synthesis of structurally diverse pyrrolidine- and tetrahydrofuran-containing organic compounds. Expected outcomes of the proposed work will include... 

In the absence of organic solvents, Sc(OTf)3 catalysed the cycloaddition of aziridines to nitriles to produce substituted imidazolines in good to excellent yields at room temperature and in an air atmosphere. The reaction is believed to progress through a highly reactive cationic intermediate in which the aziridine nitrogen is coordinated to Sc(OTf)3.65 The phosphine-catalysed enantioselective 3 + 2-cycloaddition of buta-2,3-dienoates with arylimines yielded 2-aryl-3-pyrrolidines with 64% ee.66... 

The Lewis acid-catalysed 3 + 2-cycloaddition of aziridine-2-carboxylates with isocyanates proceeds regio- and stereo-specifically to produce enantiomerically pure 4-substituted imidazolin-2-ones in high yields.33 The reaction of ethyl 7-iodo-2-heptynoate (27), 2-arylaziridines (28), and K2C03 produces polysubstituted indolizidines (30) via an S /formal 3 + 2-cycloaddition (29) process (Scheme 8).34... 

The cycloaddition of aziridines to heteromultiple bonds resulting in five-membered heterocycles has recently been studied extensively by Huisgen and his co-workers. l-(p-Methoxyphenyl)-2,3-diphenylaziridine (279)... 

The cycloaddition of aziridines to carbonyl groups has also been investigated. A recent report shows that the thermolysis of the aziridine (574) in the presence of diphenylketen gives a mixture of the pyrrolidone (575) (minor product) and the oxazolidine (576) (major product) the preferential addition to the C—C double bond is explained in terms of steric effects. Similar additions to diphenylacetaldehyde take place with the same orientation to... 

Sc(OTf) 3-catalyzed 1,3-dipolar cycloaddition reactions of phenyl aziridines with olefins such as cyclic enol ethers and allyltrimethylsilane also proceeded well [36]. Sc(OTf)3 could also be used as a catalyst for [3 + 2] cycloaddition of aziridines with various nitriles to give the corresponding imidizalines in good to excellent yields under solvent-free conditions (Scheme 12.20) [37]. Although a relatively large amount of Sc (OTf) 3 was used in this reaction, the fast reaction rate, mild conditions and experimental operational ease are the features of this system. 

Experimental procedure for the [3+3] cycloaddition of aziridine 118 Preparation of 0.14-M palladium catalyst To a... 

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