Ylides 1,3-dipolar

A highly atom-efficient azomethine ylide 1,3-dipolar cycloaddition of compound 204 (Scheme 37) with yhdes formed in situ from either proline, phenylglycine or... 

An enantioselective version of the above reactions has been reported. Lewis acids such as Yb(OTf)3 can profoundly affect the stereochemical outcome of the carbonyl ylide 1,3-dipolar cycloadditions [137]. This provided an indication to effect asymmetric carbonyl ylide cycloaddition using a chiral Lewis acid. The first example of such asymmetric induction using the chiral lanthanide catalysts has been reported [138,139]. For example, the reaction of diazoacetophenone 89 with benzyloxyacetaldehyde, benzyl pyruvate and 3-acryloyl-2-oxazoHdinone in the presence of chiral 2,6-bis(oxazolinyl)pyridine ligands and scandium or ytterbium complexes furnished the corresponding cycloadducts 165-167 with high enantioselectivity (Scheme 53). 

Sol 1. (a) The treatment of A-p-nitrobenzylbenzimidoyl chloride with trie-thylamine gives the nitrile ylide (1,3-dipolar species). The dipole is then trapped with ethyl propiolate by [3 + 2] cycloaddition reaction. 

Keywords Aromatic aldehydes, glycinemethyl ester hydrochloride, potassium carbonate, diethylzinc, N-methylmaleimide, grinding, room temperature, azomethine ylides, 1,3-dipolar cycloaddition, substituted pyrrolodines, stereoselectivity... 

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