Detail of "78008-36-3"

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1,3-Dipolar cycloaddition reactions of azomethine ylides on enantiomerically pure (E)-g-alkoxy-a,b-unsaturated esters

1,3-Dipolar cycloaddition reactions of azomethine ylides on enantiomerically pure (E)-g-alkoxy-a,b-unsaturated esters. Annunziata, Rita; Cinquini, Mauro; Cozzi, Franco; Raimondi, Laura; Pilati, Tullio (Dip. Chim. Org. Ind., Univ. Milano, Milan 20133, Italy). Tetrahedron: Asymmetry, 2(12), 1329-42 (English) 1991.Several reagents with their cas registry numbers 78008-36-3 and 126079-16-1 are used here. CODEN: TASYE3. ISSN: 0957-4166. DOCUMENT TYPE: Journal CA Section: 27 (Heterocyclic Compounds (One Hetero Atom)) Section cross-reference(s): 75 Enantiomerically pure (E)-g-alkoxy-a,b-unsatd. esters were reacted with azomethine ylides obtained from glycine imines in the presence of LiBr and diazabicycloundecene (DBU), to afford tetrasubstituted pyrrolidines with complete regiocontrol and fair to excellent diastereoselectivity (only two diastereoisomers formed in up to 96: 4 diastereoisomeric ratio). Thus, reaction of PhCH:NCH2CO2Me with (S),(E)-MeCH(OH)CH:CHCO2Me in the presence of DBU and LiBr in THF gave pyrrolidines I and II in 24% yield ( diastereoisomeric ratio). The abs. configuration of I was established by means of an x-ray crystal structure. The results are compared with those of other 1,3-dipolar cycloaddns., and the origin of stereocontrol is discussed. .