A practical improvement of crystallization-induced asymmetric transformation of allene-1,3-dicarboxylates
摘要:
Enantiomerically pure allene-1,3-dicarboxylates were easily synthesized by using epimerization-crystallization of dissymmetric allene compounds, which were prepared from acetone-1,3-dicarboxylates and naturally abundant chiral alcohols, that is, (-)and (+)-menthols, borneol, and isoborneol. After scrutinizing the crystallization of several allene-1,3-dicarboxylates in the presence of triethylamine, it was found that allene-1,3-dicarboxylate carrying bornyl groups was the most easily prepared as a single isomer because of it having suitable solubility to be crystallized in hexane at 0 degrees C to room temperature. Diels-Alder reaction of the enantiomerically pure allene-1,3-dicarboxylates and cyclic dienes, such as N-Boc-pyrrole and cyclopentadiene, afforded endo-adducts having the same configurations at two newly generated stereogenic centers. (c) 2006 Elsevier Ltd. All rights reserved.
A practical improvement of crystallization-induced asymmetric transformation of allene-1,3-dicarboxylates
摘要:
Enantiomerically pure allene-1,3-dicarboxylates were easily synthesized by using epimerization-crystallization of dissymmetric allene compounds, which were prepared from acetone-1,3-dicarboxylates and naturally abundant chiral alcohols, that is, (-)and (+)-menthols, borneol, and isoborneol. After scrutinizing the crystallization of several allene-1,3-dicarboxylates in the presence of triethylamine, it was found that allene-1,3-dicarboxylate carrying bornyl groups was the most easily prepared as a single isomer because of it having suitable solubility to be crystallized in hexane at 0 degrees C to room temperature. Diels-Alder reaction of the enantiomerically pure allene-1,3-dicarboxylates and cyclic dienes, such as N-Boc-pyrrole and cyclopentadiene, afforded endo-adducts having the same configurations at two newly generated stereogenic centers. (c) 2006 Elsevier Ltd. All rights reserved.
Enantiomerically pure allene-1,3-dicarboxylates were easily synthesized by using epimerization-crystallization of dissymmetric allene compounds, which were prepared from acetone-1,3-dicarboxylates and naturally abundant chiral alcohols, that is, (-)and (+)-menthols, borneol, and isoborneol. After scrutinizing the crystallization of several allene-1,3-dicarboxylates in the presence of triethylamine, it was found that allene-1,3-dicarboxylate carrying bornyl groups was the most easily prepared as a single isomer because of it having suitable solubility to be crystallized in hexane at 0 degrees C to room temperature. Diels-Alder reaction of the enantiomerically pure allene-1,3-dicarboxylates and cyclic dienes, such as N-Boc-pyrrole and cyclopentadiene, afforded endo-adducts having the same configurations at two newly generated stereogenic centers. (c) 2006 Elsevier Ltd. All rights reserved.