in Wiley Online Library (wileyonlinelibrary.com).An atom economic and facile synthesis of novel dispiro-oxindole-pyrrolidines has been achieved via a three-component tandem cycloaddition of azomethine ylide generated in situ from isatin and sarcosine by decarboxylative condensation with N-aryl-3-benzylidene-pyrrolidine-2,5-dione derivatives as dipolarophiles. The salient features of synthetic procedure are characterized by the mild reaction conditions, high yields, high regioselectivity and stereoselectivity, one-pot procedure, and operational simplicity. This regioselectivity was assumed to be under the influence of π-π stacking interactions between the aromatic rings of azomethine ylide and N-aryl-3-benzylidene-pyrrolidine-2,5-diones that further control the exo-endo selectivity of the reaction 1,3-dipolar cycloaddition. The regiochemistry and structures of the cycloadducts were determined with spectroscopic data.

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Cycloaddition of C,N‐diphenylnitrones 1 to N‐aryl maleimides 2 afforded two diastereomeric isoxazolidines with high selectivity. The structure and steric configuration of the adducts have been assigned on the basis of 1H NMR, 1H NMR COSY, 13C NMR and IR spectroscopy. The π–π stacking interactions between maleimide's and nitrone's aromatic rings during the 1,3‐dipolar cycloaddition were assumed to control the exo–endo selectivity of the reaction. Thus, the exo–endo ratio depends upon the position of the substituent present on the C‐phenyl ring of the C,N‐diphenylnitrones.

KAUR, A.; KAUR, M.; SINGH*, B.; J. Heterocycl. Chem. 52 (2015) 3, 827-833, http://dx.

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