Azetidinone intermediates for the synthesis of cephem ring systems. Part 1. Chemical shift non-equivalence of the allylic methylene protons

Vigevani, A.; Foglio, Maurizio; Franceschi, Giovanni; Masi, Paolo; Suarato, Antonino; Gandini, E.; Palamidessi, G.

doi:10.1039/p19790000504

Cited by 5 publications

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“…In a recent publication dealing with compounds of type 30, the Farmitalia group have observed (19) that, for certain combinations of E and Z, the 'A multistep process, involving Michael addition of acetate to the conjugated ester to form i. followed by displacement of bromine and elimination of acetate, might also be proposed. This seems unlikely for three reasons: (i) we have been unable to observe conjugate addition to compounds of type 3 under a variety of conditions; (ii) the 0-elimination of acetate is expected and 30 (E = OAc, Z = Br) each showed singlets for both methylene groups.…”

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Sulfur-free penicillin derivatives. VII. Multiple functionalization of 2-azetidinyl-3-methyl-2-butenoates

Wolfe¹,

Shaw²

1982

Can. J. Chem.

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SAUL WOLFE and CHIA-CHENG SHAW. Can. J. Chem. 60, 144 (1982). The title compounds, substituted with chlorine in the 4'-position and with phthalimido, 2,2,2-trichloroethoxycarbonylamino, or phenoxycarbonylamino in the 3'-position of the azetidinone ring, have been converted to bis-allylic formates via bromination of both methyl groups with excess N-bromosuccinimide, and displacement of both bromines by formate ions in methylene chloride solvent. The diformates react smoothly with a deficit of a boron halide to form EIZ mixtures of halogeno-formates, in which the E-isomer predominates. Depending on the 3'-azetidinyl substituent, these halogeno-formates undergo a second displacement with acetate either with retention of olefinic geometry or inversion of olefinic geometry. The mechanisms of these reactions are discussed, along with further transformations leading to hydroxylactones, halogenolactones, halogenohydrins, and other compounds. Examination of the proton magnetic resonance spectra of twenty-one compounds reveals that methylene protons cis to the p-lactam nitrogen atom of a methyl 2-azetidinyl-2-butenoate are found at higher field than methylene protons cis to the methoxycarbonyl group. This observation appears to provide a more reliable criterion for the assignment of configuration to geometrical isomers than one based on the magnitude of the chemical shift nonequivalence of the E and Z methylene protons.SAUL WOLFE et CHIA-CHENG SHAW. Can. J. Chem. 60, 144 (1982). Le compose mentionne dans le titre portant une chlore en position 4' et un groupe phtalimido, trichloro-2,2,2 ethoxycarbonylamino ou phenoxycarbonylamino en position 3' du cycle azetidinone, soumis a une bromation des groupes methyles au moyen d'un exces de N-bromosuccinimide suivie par deplacement des bromes par des ions formiates dans le chlorurc de methyli-ne, conduit aux formiates his-allyliques. Les diformiates reagissent avec un defaut d'halogenure de bore en donnant les melanges EIZ d'halogenofonniates dans lesquels I'isomere E est majoritaire. Dkpendant du substituant en position 3' du cycle azetidinyle, ces halogenoformiates, en presence d'un acetate, subissent une deuxieme reaction de deplacernent avec retention ou inversion de la geometrie de I'olefine. On discute des rnecanismes de ces reactions ainsi que des transformation plus poussees qui conduisent a des hydroxylactones, des halogenolactones, des halohydrines et a d'autres composes. Les spectres de rmn du IH de vingt et un composes revelent que les protons methyleniques en position 6 par rapport a I'atome d'azote du p-lactame du azetidinyl-2 butene-2 oate de methyle, sont deplaces vers les champs forts par rapport aux protons methyleniques en position cis du groupe methoxycarbonyle. Ces observations semblent fournir des criteres plus surs, que ceux fondes sur I'ordre de grandeur de la non equivalence des deplacements chimiques des protons mtthyliques des isomeres E et Z, pour determiner la configuration des isomeres geometriques.[Traduit par le journal]The first synthesis of a 1-ox...

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