Effect Of Oxygen Substituents Research Articles

ChemInform Abstract: Effect of Oxygen Substituent in the Aniline Part of Benzanilide on the Regioselectivity in Direct Arylation Using Palladium‐Phosphine Reagents.

AbstractThe generality of the oxygen‐substituent effect on the coupling position is examined by the biaryl coupling reaction of benzanilides (I) and (IV), having oxygen substituents in the aniline part.

Effect of Oxygen Substituent in the Aniline Part of Benzanilide on the Regioselectivity in Direct Arylation Using Palladium-Phosphine Reagents

This study investigated the effect of oxygen substituents at the 3'-position in the aniline part of 2-iodobenzanilides on the coupling position in its Pd-assisted direct arylation. Benzanilide with methylenedioxy and acetoxy groups yielded the ortho-product formed predominantly by connection to a more hindered carbon. The mechanism is discussed from the perspectives of both steric and coordinated effects.

Synthetic Studies on Aromatic Heterocyclic Compounds

This review covers the concise synthesis of simple coumarin with salicyl aldehydes and Wittig reagent, and a convenient synthesis of polycyclic aromatic heterocyclic compounds using the aryl-aryl coupling reaction of aryl benzamides and aryl benzoates with a Pd reagent is presented. In the first section, the reactions of salicyl aldehydes with OMe, OH, Br, CO(2)Me, and NO(2) groups with carbethoxymethylenetriphenylphophorane are described. Specifically, the reaction of 3-nitrosalicylaldehyde with amines gave benzoxazoles in moderate yield. In the second section, the syntheses of benzo[c]phenanthridine alkaloids, quinazoline alkaloids, and graphislactones in the Pd-mediated biaryl coupling reaction are described. Moreover, the synthesis of benzonaphthazepine and pyrrolophenanthridine alkaloids utilizing regioselective C-H activation with intramolecular coordination of a benzylamine to Pd is described, and the effects of oxygen substituents in the benzoyl part of benzanilides on the coupling position in its biaryl coupling reaction are presented. An effective Pd reagent for the coupling reaction of aryl tolyflate and arene was developed.

MAO inhibition by arylisopropylamines: the effect of oxygen substituents at the β-position

Twenty-nine arylisopropylamines, substituted at the β-position of their side chain by an oxo, hydroxy, or methoxy group, were evaluated in vitro as MAO-A and MAO-B inhibitors. The oxo derivatives (`cathinones') were in general less active as MAO-A inhibitors than the corresponding arylisopropylamines, but exhibited an interesting MAO-B inhibiting activity, which was absent in the hydroxy, methoxy, and β-unsubstituted analogues. These results suggest that selective affinity for the two MAO isoforms in this family of compounds is modulated not only by the aryl substitution pattern but also by the side-chain substituents on the arylalkylamine scaffold.

Effect of oxygen substituents on two- and three-bond carbon-proton spin-spin coupling constants

Carbon–proton coupling constants of 12 iridoid glucosides were determined from NMR data. Proton–proton vicinal couplings, quantitative NOE and molecular modelling were used to determine the conformational behaviour of the compounds. The aglycone moiety of all the compounds included in the study were shown to be conformationally rigid. Comparison of the experimental carbon–proton couplings with the calculated geometries resulted in the quantification of the dependence of 2,3J(13C,1H) on the orientation of oxygen substituent attached to coupling pathway (ψ). This can be extended to other electronegative substituents. The effect was studied by considering the product of Si, the substituent constant at a given position, and a cosine type function of ψ, the dihedral angle between the considered oxygen substituent and the atoms of the coupling pathway. In taking into account the influence of —OR substituents at β- and γ-carbons on vicinal coupling constants (13Cα—Cβ—Cγ—1H fragment), we found that the Sicosϕ cosψ term can be applied successfully, where ϕ is the dihedral angle between coupled atoms. Copyright © 2000 John Wiley & Sons, Ltd.

Flexible molecules with defined shape. Part 5. Conformational analysis of 2,4,6,n-polymethylated alkane derivatives

Poly-2,4,6,n-methylated undecene-(3–6) and pentadecene-derivatives(8–11) have been synthesized. In these compounds each backbone segment displays local bi-conformational behaviour. The effect of oxygen-substituents on the conformer population of the individual backbone segments has been studied by evaluating 3JH,H and 3JC,C coupling constants.

Thermolysis of unsymmetrically substituted vinylcyclopropanes. Regarding the effect of oxygen substituents on the site-selectivity of homo-[1,5]-sigmatropic hydrogen migrations

Thermal rearrangement of compounds 1, 8–11, and 20 results, in each case, in the exclusive migration of the hydrogen (HΛ) not associated with the oxygen substituent. On the other hand, thermolysis of 19, 22, and 23 provides, in each case, a mixture of the two possible sigmatropic rearrangement products. Similar bond reorganization of the hydrocarbon 21 affords the dienes 27 and 28 (98:2, respectively). On the basis of these results, along with those reported earlier, it is proposed that in the transition states for these rearrangements (a) there is an accumulation of electron density at the carbon from which the hydrogen migrates, and (b) this carbon center has a planar or nearly planar geometry.