Photolyse stéréosélective des [α-tétrahydropyrannyloxy] -2 tétrahydropyrones-3

The photochemical irradiation of the 2-[sα-tetrahydropyrannyl-oxy]-3-tetrahydropyrones (3) gives the -3-tetrahydropyrone (6)and the α-valerolactone (7). the structures (S*, R*) or (S*, S*) which were determined by mmr and by comparison with the 2-[α-tetrahydropyrannyloxy]-2tetrahydropyrannes (5) (S*, R*) and (S*, S*) influence the rate of the photolysis     

Action d'organolithiens sur la méthyl-2 quinoxaline. Etude de la réactivité des adduits

The action of organolithium reagents such as phenyllithium or n-bulyllithium on 2-methylquinoxaline gave lithiation of the methyl group which upon reaction with electtropholesphiles produce side chain alkenyl derivatives. On the other hand organolithium reagents react with the quinoxaline azomethine bond to give I-lithio-2-alkyl)or ary-1)-3 methylquinoxalines which can be further loithiated on the methyl group to give 2-alkyl(or aryl)-3-alkenylquinoxaline derivatives. The adducts can be condensed with clectrophiles such as benzonitrile or methlyl benzoate but only methyl benzoate leads to N condensed derivatives. Furthermore substituted 1,2,3,4-terahydroqinoxalines are available via the above lithio intermediates.     

Synthèse du mèthyl-1 diformyl-2,3 pyrrole,de la méthyl-1 pyrrolo[2,3-d] pyridazine et de la méthyl-1 oxo-6 (6h)cycloheptatrieno[b] pyrrole

This communication describes the synthesis of l-methyl-2,3-diformylpyrrole. This new compound is used to prepare a new heterocycle, l-methylcyclohepta[b]pyrrol-6-one and thus allows a new synthesis of l-methylpyrrolo[2,3-d]pyridazine.     

Synthèse et stéréochimie de perhydrocyclopenta[b]furannones-3-cis et perhydrocyclopenta[b]furannols-3-cis

Synthetic route to new cis-perhydrocyclopenta[b]furan-3-ones and cis-perhydrocyclopenta[b]furan-3-ols is described. Their configurations and conformations were inferred by ¹H and ¹³C nmr spectroscopy. A certain rigidity is associated with the bond common to the two fused ring. The conformation of tetrahydrofuran-3-one ring appears to be a composite of the C, and C₂ forms depending on the C-2 substitution.     

Etude Stéréochimique par RMN 1H de Tetrahydropyrannes β-Chlorés α-Substitués

The ¹H NMR study of 2-alkyl-3-chlorotetrahydropyrans, obtained by reaction of Grignard reagents with a mixture of cis/trans-2,3-dichlorotetrahydropyrans, shows cis/trans configuration of two isomers in which the alkyl substituents are exclusively in the equatorial position. 3-Chloro-2-phenyltetrahydropyran exists in trans (eq-eq) configuration only. The ¹H NMR study of cis/trans 2-alkoxy (or aryloxy)-3-chlorotetrahydropyrans, obtained by reaction of alcohols or phenol with 2,3-dichlorotetrahydropyrans, shows the axial position of the alkoxy (or aryloxy) substituent.     

Formation d'hydroxy-5 méthyl-5 isoxazolidinones-3 par action du dicétène sur les hydroxylamines

The reaction of diketene with N-monosubstituted hydroxyl-amines provides cyclic derivatives of the 5-hydroxy-5-methyl-isoxazolidin-3-one type.