The Rh4(CO)12-catalyzed hydroformylation at low temperature (40°C) of the 1-, 2- and 3-vinylpyrrole gives the corresponding branched aldehydes 2-(1-pyrrolyl)propanal, 2-(2-pyrollyl)propanal and 2-(3-pyrrolyl)propanal with high α-regioselectivity.
A newgeneral de novo synthesis of pharmaceutically important α-aryl β-perfluoroalkyl ketones has been disclosed. Compared with trifluoromethylation-initiated radical 1,2-aryl migration of α,α-diaryl allylic alcohols, this protocol employs a new strategy of biomimetic carbene catalysis to assemble alkene, aldehyde and perfluoroalkyl reagents, providing access to products with excellent flexibility
The influence of the temperature on the regioselectivity in the hydroformylation of the vinylpyrrole isomers and of the corresponding N-tosylated substrates has been investigated in the range 20-100 degrees C, in the presence of Rh-4(CO)(12). Ar all the temperatures the branched aldehyde was prevailing with respect to the linear isomer for all the substrates (I cu-regioselectivity). With increasing temperature, an increase of the linear aldehyde was observed to a different extent in dependence on the substrate nature. H-2 NMR investigation of the crude reaction mixture recovered from deuterioformylation of 3-vinylpyrrole at partial substrate conversion points out that the observed depression of the alpha-regioselectivity with increasing temperature must be connected to a beta-hydride elimination process occurring for the branched alkyl-rhodium intermediates but not for the linear ones. (C) 1997 Elsevier Science S.A.
Asymmetric Organocatalytic Synthesis of Bisindoles - Scope and Derivatizations
作者:Christina Retich、Stefan Bräse
DOI:10.1002/ejoc.201701502
日期:2018.1.10
library of various novel biologically active bisindoles with different substitution patterns was synthesized. Electro‐withdrawing groups on the starting material led to the formation of Povarov‐type structures. Furthermore we could successfully demonstrate that consecutive reactions like cross couplings, reductions or even click reactions on bisindoles are feasible.