998 resultados para 030500 ORGANIC CHEMISTRY
Resumo:
Zn/acetic acid reaction of DDHQ esters 1 a-d gave the saturated acids 3 a-d and the hydrocarbons 7 a-d. The intermediacy of the aldehydes 10 and 11 in the formation of the products has been established. Oxidation of hydrocarbons 7a and 7b gave the corresponding tropones (5a and 5b).
Resumo:
PMR spectra of carbonyl compounds 2a-k reveal significant variations in the population of E and Z isomers on changing the solvent from CDCl3 to DMSO-d6. In non-polar media, the intramolecular N-H…. O hydrogen bonded form is exclusively observed. In DMSO-d6, the alternative Z form is also populated. A similar conformational switch is also noted in the corresponding thiones. Different interpretations are critically analysed. The most consistent explanation is suggested to involvean interplay of N-H….X hydrogen bonding and S…X attractive interaction (X = O,S) in these systems. Ab initio calculations support this interpretation.
Resumo:
A four step cyclopentaannulation methodology starting from allyl alcohols using 5-exo-trig radical cyclisation as the key reaction, and its application to the total synthesis of 4-epibakkenolide is described.
Resumo:
beta-Cyclodextrin borate catalyses oxygenation of aryl substituted alkenes in the presence of t-BuOOH to afford beta-dioxy alcohols in good yields (63-86%). Copyright (C) 1996 Published by Elsevier Science Ltd
Resumo:
Potassamide induced in situ alkylation of 4-cyano-3-methoxy-1-methyl-5, 6-dihydroisoquinoline (1a) with allyl bromide gives the 5-allyl- and 5,9-diallyl-5,6-dihydroisoquinolines (1c and 1d), isoquinoline derivative 2 and 4-allyl-1, 2, 3, 4-tetrahydroisoquinolin-3(2H)-one (3a). However, potassamide induced in situ alkylation of In with buten-2-one, mesityl oxide and acrylonitrile results in the formation of only 5-alkylated 5,6-dihydroisoquinoline derivatives 1e-g along with fully aromatised compound 2.
Resumo:
A regiospecific reduction of quinolines (and 1,10-phenanthroline) into the corresponding 1,2,3,4-tetrahydro derivatives using a combination of sodium cyanoborohydride and boron trifluoride etherate in refluxing methanol is described. Under the same conditions indole and acridine reduced to the corresponding dihydroderivatives, whereas acyl group transfer from oxygen to nitrogen atom is also noticed in the case of 8-acyloxyquinolines.
Resumo:
Micelles of different dimeric amphiphiles Br-, n-C(16)H(33)NMe(2)(+) -(CH)(m)-N(+)Me(2)-n-C16H33, Br- (where m = 3, 4, 5, 6, 8, 10, and 12) adapt different morphologies and internal packing arrangements in aqueous media depending on their spacer chain length (m). Detailed measurements of small angle neutron scattering (SANS) cross sections from different bis-cationic, dimeric surfactant micelles in aqueous media (D2O) are reported. The data have been analyzed using the Hayter and Penfold model for macro ion solution to compute the interparticle structure factor S(Q) taking into account the screened Coulomb interactions between the dimeric micelles. The SANS analysis clearly indicated that the extent of aggregate growth and the variations of shapes of the dimeric micelles depend primarily on the spacer chain length. With spacer chain length, m less than or equal to 4, the propensity of micellar growth was particularly pronounced. The effects of the variation of the concentration of dimeric surfactants with m = 5 and 10 on the SANS spectra and the effects of the temperature variation for the micellar system with m = 10 were also examined. The critical micelle concentrations (cmc) and their microenvironmental feature, namely, the microviscosities that the dimeric micellar aggregates offer to a solubilized, extrinsic fluorescence probe, 1,6-diphenyl-1,3,5-hexatriene, were also determined. The changes of cmcs and microviscosities as a function of spacer chain length have been explained in terms of conformational variations and progressive looping of the spacer in micellar core upon increasing m values.
Resumo:
A strategy for the synthesis of new macrocycles built on 7-deoxycholic acid is described.