Fluorine gas for life science syntheses: green metrics to assess selective direct fluorination for the synthesis of 2-fluoromalonate esters
作者:Antal Harsanyi、Graham Sandford
DOI:10.1039/c5gc00402k
日期:——
Green metric assessment of the one step synthesis of 2-fluoromalonate esters using fluorine gas compares favourably with established multistep processes.
使用氟气一步合成2-氟丙二酸酯的绿色度量评估与已建立的多步方法相比具有优势。
Direct fluorination of 1,3-dicarbonyl compounds
作者:Richard D. Chambers、Martin P. Greenhall、John Hutchinson
DOI:10.1039/c39950000021
日期:——
1,3-Dicarbonyls, such as 1,3-diketones and 1,3-ketoesters, react directly with elemental fluorine at room temperature to give the corresponding 2-fluoro- and, in some cases, 2,2-difluoro-compounds in high yield.
Diethyl fluoromalonate was prepared in one-pot from chlorotrifluoroethene via trifluoroacrylic acid lithium salt in 79% yield. Diethyl fluoromalonate was easily converted to 5-fluoro-6-chlorouracils, reductions of which gave 5-fluorouracils in good yields.
Source regions and timescales for the delivery of water to the Earth
作者:A. Morbidelli、J. Chambers、J. I. Lunine、J. M. Petit、F. Robert、G. B. Valsecchi、K. E. Cyr
DOI:10.1111/j.1945-5100.2000.tb01518.x
日期:2000.11
Abstract—In the primordial solar system, the most plausible sources of the water accreted by the Earth were in the outer asteroid belt, in the giant planet regions, and in the Kuiper Belt. We investigate the implications on the origin of Earth's water of dynamical models of primordial evolution of solar system bodies and check them with respect to chemical constraints. We find that it is plausible that the Earth accreted water all along its formation, from the early phases when the solar nebula was still present to the late stages of gas‐free sweepup of scattered planetesimals. Asteroids and the comets from the Jupiter‐Saturn region were the first water deliverers, when the Earth was less than half its present mass. The bulk of the water presently on Earth was carried by a few planetary embryos, originally formed in the outer asteroid belt and accreted by the Earth at the final stage of its formation. Finally, a late veneer, accounting for at most 10% of the present water mass, occurred due to comets from the Uranus‐Neptune region and from the Kuiper Belt. The net result of accretion from these several reservoirs is that the water on Earth had essentially the D/H ratio typical of the water condensed in the outer asteroid belt. This is in agreement with the observation that the D/H ratio in the oceans is very close to the mean value of the D/H ratio of the water inclusions in carbonaceous chondrites.