Manganese‐Catalyzed Multicomponent Synthesis of Pyrroles through Acceptorless Dehydrogenation Hydrogen Autotransfer Catalysis: Experiment and Computation
作者:Jannik C. Borghs、Luis Miguel Azofra、Tobias Biberger、Oliver Linnenberg、Luigi Cavallo、Magnus Rueping、Osama El‐Sepelgy
DOI:10.1002/cssc.201802416
日期:2019.7.5
A new base metal catalyzed sustainable multicomponent synthesis of pyrroles from readily available substrates is reported. The developed protocol utilizes an air‐ and moisture‐stable catalyst system and enables the replacement of themutagenic α‐haloketones with readily abundant 1,2‐diols. Moreover, the presented method is catalytic in base and the sole byproducts of this transformation are water and
alkyl substrates were efficiently converted in combination with different type of amines and vicinal diols into various substituted pyrroles in reasonable to excellent isolated yields. Additionally, α-functionalized ketones gave synthetically interesting amido-, alkoxy-, aryloxy-, and phosphate-substituted pyrroles in a straightforward manner. The synthetic protocol proceeds in the presence of a commercially
O-(2-hydroxyethyl)hydroxylamine could be converted to 4 upon the exchange of the –OH with iodine and subsequent cyclization by t-BuOK in t-BuOH in good yield. Tetrahydroindole (4) itself is very unstable, requiring storage in a freezer under N2. 3 Furthermore, C-N bond formation is an additional step which requires the use of a transition metal catalyst. Therefore, a shorter procedure in which the N-aryl