A study on the metalation of alkoxydibromobenzenes
摘要:
The metalation of (quasi)alkoxy-substituted dibromobenzenes C6H3(OR)Br-2 with lithium diisopropylamide (LDA) has been investigated. For 1-(quasi)alkoxy-3,5-dibromobenzenes (R = Me, TMS), different selectivities were observed depending on reaction conditions and the size of the alkoxy group. The methoxy group was an effective ortho-director whereas this was not the case for the bulky trimethylsilyloxy group. The metalation of related 2,5-dibromoanisole was also examined showing a significant meta-directing effect by the methoxy group. The thermal stability of aryllithium intermediates is significantly lower when lithium is flanked by a bromine and a methoxy group, whereas 4-(quasi)alkoxy-2,6-dibromoaryllithiums are less labile. (c) 2005 Elsevier Ltd. All rights reserved.
A study on the metalation of alkoxydibromobenzenes
摘要:
The metalation of (quasi)alkoxy-substituted dibromobenzenes C6H3(OR)Br-2 with lithium diisopropylamide (LDA) has been investigated. For 1-(quasi)alkoxy-3,5-dibromobenzenes (R = Me, TMS), different selectivities were observed depending on reaction conditions and the size of the alkoxy group. The methoxy group was an effective ortho-director whereas this was not the case for the bulky trimethylsilyloxy group. The metalation of related 2,5-dibromoanisole was also examined showing a significant meta-directing effect by the methoxy group. The thermal stability of aryllithium intermediates is significantly lower when lithium is flanked by a bromine and a methoxy group, whereas 4-(quasi)alkoxy-2,6-dibromoaryllithiums are less labile. (c) 2005 Elsevier Ltd. All rights reserved.
Selective recovery of a pyridine derivative from an aqueous waste stream containing acetic acid and succinonitrile with solvent impregnated resins
作者:J. Bokhove、T.J. Visser、B. Schuur、A.B. de Haan
DOI:10.1016/j.reactfunctpolym.2014.11.007
日期:2015.1
Solvent impregnated resins (SIRs) were evaluated for the recovery of pyridine derivatives from an aqueous waste-stream containing also acetic acid and succinonitrile. For this purpose, a new solvent was developed, synthesized and impregnated in Amberlite XAD4. Sorption studies were used to determine the capacity, selectivity and the mass-transfer rate. A high capacity of 21 g 4-cyanopyridine (CP) per kg SIR was found, with very high selectivity toward CP over the other solutes of at least 570. A modified Langmuir equation could describe the equilibrium sorption isotherm. Both the linear driving force model and a Fickian diffusion model were evaluated. The Fick-model described both regeneration and loading best. The CP-diffusivity through the solvent phase was estimated at 6.53.10(-13) +/- 2.5% m(2) s(-1). The model was validated using fixed-bed column experiments. The R-2 values for this model ranged between 0.94 at a flow rate of 5 mL/min and 0.99 at a flow rate of 1 mL/min during the loading cycle. Due to mass-transfer limitations the breakthrough profiles were broad and breakthrough occurred after 5 or 23 bed volumes, for flow rates of 5 and 1 mL/min, respectively. Both acetic acid and succinonitrile broke through immediately due to the very high CP-selectivity of the SIR. (C) 2014 Elsevier B.V. All rights reserved.
A study on the metalation of alkoxydibromobenzenes
The metalation of (quasi)alkoxy-substituted dibromobenzenes C6H3(OR)Br-2 with lithium diisopropylamide (LDA) has been investigated. For 1-(quasi)alkoxy-3,5-dibromobenzenes (R = Me, TMS), different selectivities were observed depending on reaction conditions and the size of the alkoxy group. The methoxy group was an effective ortho-director whereas this was not the case for the bulky trimethylsilyloxy group. The metalation of related 2,5-dibromoanisole was also examined showing a significant meta-directing effect by the methoxy group. The thermal stability of aryllithium intermediates is significantly lower when lithium is flanked by a bromine and a methoxy group, whereas 4-(quasi)alkoxy-2,6-dibromoaryllithiums are less labile. (c) 2005 Elsevier Ltd. All rights reserved.