Reduction of Pyrrolyl- and Indolylamides with BH<sub>3</sub>·THF: Cyclodeoxygenation versus Deoxygenation
作者:Kelin Li、Jon A. Tunge
DOI:10.1021/jo801627z
日期:2008.11.7
Herein we report that borane reductions of acylpyrroles and acylindoles that contain a pendant phenol take two different paths. Acylpyrroles undergo a reductive cyclization to make unusual chromanyl pyrroles. Treatment of related acylindoles under identical conditions results in deoxygenation without cyclization. The results are interpreted in terms of relative rates of cyclization and reduction of intermediate carbenium ions, where cyclization of the indole-stablized carbenium ion is slower.
A convenient synthesis of dihydrocoumarins from phenols and cinnamic acid derivatives
A facile procedure for synthesis of dihydrocoumarin derivatives was described. Although the yield of the products in the reaction of phenols with acrylates in trifluoroacetic acid in the presence of Pd(OAc)2 giving coumarins was found to be very low, dihydrocoumarin derivatives were obtained in good to high yields in the absence of Pd(OAc)2 when ethyl cinnamates bearing electron-donating groups were
Stereochemical Control in the Reduction of 2-Chromanols
作者:Kelin Li、Kumar Vanka、Ward H. Thompson、Jon A. Tunge
DOI:10.1021/ol061727g
日期:2006.10.1
silane reductants and 2,4-trans-chromans using the smaller silane PhSiH(3). The stereochemical outcome has been rationalized on the basis of a Curtin-Hammett kinetic situation arising from hydride delivery to two different conformations of an intermediate oxocarbenium ion. This method provides a powerful way to control the relative stereochemistry of these substructures which are prevalent in bioactive