Double diastéréosélectivité de la cycloaddition dipolaire-1,3 d'ylures d'azométhine cycliques substitués

Abstract

R e p le 27 juillet 1993 TAHAR LAKHLIFI, AHMED SEDQUI, TOUFIK FATHI, BERNARD LAUDE et JEAN-FRAN~OIS ROBERT. Can. J. Chem. 72,1417 (1994. La synthkse de sept 5-ph~nyl-3,4-dihydro-2H-pyrrole-2-carboxylates de mCthyle precurseurs d'ylures d'azomCthine cycliques pentagonaux 1 est dkcrite. Ces produits i caractere dipolaire rkagissent avec les N-methyl et N-phCnylmal6imides de fa~on diastCrCospCcifique. L'approche des reactants se fait sur la face la moins encombrke du dip81e-1,3 et en endo pour donner le cycloadduit thermodynamiquement le plus stable de structure exo. De plus, l'oxydation de ces composes 1 permet d'acceder aux pyrroles substituCs correspondants.TAHAR LAKHI~FI, AHMED SEDQUI, T o m FATHI, BERNARD LAUDE, and JEAN-FRAN~OIS ROBERT. Can. J. Chem. 72, 1417Chem. 72, (1994. Seven derivatives of methyl 5-phenyl-3,4-dihydro-2H-pyrrole-2-carboxylates 1 were synthetized. These compounds are precursors of pentagonal cyclic azomethine ylids, the two sides of which are diastereotopic. The 1,3-dipolar species react with N-methyl and N-phenylmaleimides diastereospecifically. The approach of the reactant species occurs from the less hindered side of the 1,3-dipole and in endo to lead the thermodynamically stable exo cycloadduct. Moreover, oxidation of the compounds 1 gives the corresponding substituted pyrroles.

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

“…In this case, the nitrile group remains in the products and 3,5-disubstituted pyrrole-2-carbonitriles 10 are obtained. Tsuge et al reported the oxidation of pyrroline-3-carboxylates with chloranil [ 45 ] while pyrrole-2-carboxylates were obtained from the oxidation of pyrroline-2-carboxylate with chloranil [ 46 – 47 ] or DDQ [ 48 ]. Different oxidants were screened for the oxidation of cyanopyrroline 6a to pyrrole 10a and the results were judged by TLC.…”

Chemistry of 7-Azabicyclo[2.2.1]hepta-2,5-dienes, 7-Azabicyclo[2.2.1]hept-2-enes, and 7-Azabicyclo[2.2.1]heptanes

“…121 This stereochemistry was rationalized to be the result of an endo transition state. 122 A one-pot reaction of the pyrollidine 121 with a mixture of AgF and phenyl vinyl sulfone in dry acetonitrile under an argon atmosphere at room temperature gave cycloadduct 122 in 90% yield (Scheme 29). 123 This reaction proceeded via [3+2] cycloaddition of the transient cyclic azomethine ylide with the dipolarophile.…”

“…The 5-phenyl-2-methoxycarbonyl-3,4-dihydro-2 H -pyrrole derivatives 119 have been shown to tautomerize in refluxing toluene to afford cyclic azomethine ylides, which react with N- phenylmaleimide 115b to give the [3+2] cycloadducts 120 . , The stereochemistry of the reaction was established by X-ray crystallography of the adduct 120 (Scheme ) . This stereochemistry was rationalized to be the result of an endo transition state 28 …”

Pyrrolodiazines. 5. Synthesis, Structure, and Chemistry of Pyrrolo[1,2-c]pyrimidine. Dipolar Cycloaddition of Pyrrolo[1,2-c]pyrimidinium Ylides

“…With respect to the stereoselectivity observed, the reaction of 20 with mono- and disubstituted olefinic dipolarophiles preferred the endo approach of the dipolarophile and the ylide, which seems to react through the anti form in all cases. The exclusive participation of the anti form 24 of the ylide is related to the well-established higher stability of this form over the syn one, when ylides are stabilized by a carbonyl group …”