Synthesis of C5-Substituted Imidazolines. -The pharmacologically interesting title compounds are prepared by Mitsunobu reaction of the 5-hydroxymethyl derivative (II) with aromatic alcohols or N-nucleophiles. The imidazoline (III) is prepared in 4 steps from 2,3-diaminepropionic acid (I) in excellent overall yield. -(DEFACQZ, N.; TRAN-TRIEU, V.; CORDI, A.; MARCHAND-BRYNAERT*, J.; Tetrahedron Lett. 44 (2003) 51, 9111-9114; Unite Chim. Org. Med., Univ. Cathol. Louvain, B-1348 Louvain-la-Neuve, Belg.; Eng.) -Mais 13-091
N-Buta-1,3-dienylsuccinimide 1 reacts quantitatively with trimethyl 2-phosphonoacrylate 2a to furnish the ortho-[4 ϩ 2]-cycloadduct 3a as a single stereoisomer. The cis axial/equatorial relationship between the succinimido and phosphonate groups respectively has been established by NMR and X-ray diffraction analyses. Triethyl 2-phosphonoacrylate 2b similarly undergoes cycloaddition with the diene 1 to give a 55 : 45 mixture of ortho stereoisomers 3b (cis axial/equatorial) and 4b (trans axial/axial). The activating and directing effect of the phosphonate group is discussed on the basis of a theoretical approach considering the van der Waals complexes.
Vinyl phosphonates -substituted with carboxylate, nitrile, sulfone and phosphonate groups reacted with N-buta-1,3dienylsuccinimide to give [4 2] ortho-cycloadducts as mixtures of endo/exo stereoisomers.
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