for the ortholithiation of 3-aryl and 3-styryl furans has been uncovered wherein lithiation occurs preferentially at the sterically encumbered 2-position. The results are attributed, at least in part, to stabilization of the intermediate furyl anion by through-space donation of pi-electron density from the substituent appended at the 3-position to the lithium cation. This ortholithiation reaction
Cationic Gold(I)-Mediated Intramolecular Cyclization of 3-Alkyne-1,2-diols and 1-Amino-3-alkyn-2-ols: A Practical Route to Furans and Pyrroles
作者:Masahiro Egi、Kenji Azechi、Shuji Akai
DOI:10.1021/ol901942t
日期:2009.11.5
The intramolecular cyclizations of the 3-alkyne-1,2-diols and the 1-amino-3-alkyn-2-ols with a low catalyst loading (0.05-0.5 mol %) of (Ph3P)AuCl-AgNTf2 or (Ph3P)AuCl-AgOTf proceeded at room temperature to provide a variety of substituted furans and pyrroles in excellent yields (85-98% yields). This method is also fully applicable to the conversion of several dozen grams of the substrate using only 0.05 mol % each of the Au and Ag catalysts.
Synthesis and insect antifeedant activity of 2-substituted 2,3-dihydrofuran-3-ols and butenolides (Part II)
作者:Edwin A klein Gebbinck、Gerrit A Stork、Ben J.M Jansen、Aede de Groot
DOI:10.1016/s0040-4020(99)00612-2
日期:1999.9
Enantioselective Oxidative (4+3) Cycloadditions between Allenamides and Furans through Bifunctional Hydrogen-Bonding/Ion-Pairing Interactions
作者:Laura Villar、Uxue Uria、Jose I. Martínez、Liher Prieto、Efraim Reyes、Luisa Carrillo、Jose L. Vicario
DOI:10.1002/anie.201704804
日期:2017.8.21
N‐trifluoromethanesulfonyl phosphoramides catalyze the enantioselective (4+3) cycloaddition between furans and oxyallyl cations, the latter being generated in situ by oxidation of allenamides. The chiral organic phosphoramide counteranion is proposed to engage in the activation of the oxyallyl cation intermediate through cooperative hydrogen‐bonding and ion‐pairing interactions, enabling an efficient chirality