Zn(II)-Catalyzed Addition of Aromatic/Heteroaromatic C(sp<sup>2</sup>)–H to Azoalkenes: A Polarity-Reversed Arylation of Carbonyl Compounds
作者:Cecilia Ciccolini、Lucia De Crescentini、Fabio Mantellini、Stefania Santeusanio、Gianfranco Favi
DOI:10.1021/acs.orglett.9b01628
日期:2019.6.7
An umpolung α-(hetero)arylation strategy that involves the Michael-type reaction between electron-rich (hetero)aromatic substrates and azoalkenes is developed. The reaction proceeds under very mild conditions at room temperature and in the presence of inexpensive, nontoxic ZnCl2 catalyst to provide access to otherwise inaccessible hydrazone structures. Subsequent hydrolysis of these latter to ketones
Substrate-controlled reactions have been developed for the synthesis of spirocyclopropylpyrazolones and bicyclic 4,5-dihydropyrazoles from 1,2-diaza-1,3-dienes and sulfur ylides. These protocols were carried out under mild reaction conditions without any additives in generally moderate to good yields. Plausible mechanisms for the transformations were proposed.
Divergent base-induced reactivity of cycloalkenyl-1-diazenes
作者:Orazio A. Attanasi、Stefano Berretta、Lucia De Crescentini、Gianfranco Favi、Paolino Filippone、Gianluca Giorgi、Fabio Mantellini
DOI:10.1016/j.tet.2010.06.061
日期:2010.8
The different base-promoted regioselectivities of the ring closure processes in the reactions between cycloalkenyl-1-diazenes and beta-ketoesters are investigated. Under the appropriate conditions it is possible to turn the synthesis towards cycloalkenyliden-pyrroles or functionalized 3-hydroxy-hydrocinnolines. The aromatization procedure of the heteroring counterpart of the 3-hydroxy-hydrocinnolines is also reported. (C) 2010 Elsevier Ltd. All rights reserved.
Synthesis of Polycyclic Fused Indoline Scaffolds through a Substrate-Guided Reactivity Switch
作者:Cecilia Ciccolini、Giacomo Mari、Francesco G. Gatti、Giuseppe Gatti、Gianluca Giorgi、Fabio Mantellini、Gianfranco Favi
DOI:10.1021/acs.joc.0c01489
日期:2020.9.4
Zn(II)-catalyzed divergent synthesis of functionalized polycyclic indolines through formal [3 + 2] and [4 + 2] cycloadditions of indoles with 1,2-diaza-1,3-dienes (DDs) is reported. The nature and type of substituents of substrates are found to act as a chemical switch to trigger two distinct reaction pathways and to obtain two different types of products upon the influence of the same catalyst. The mechanism of both [4 + 2] and [3 + 2] cycloadditions was investigated and fully rationalized by density functional theory (DFT) calculations.