Alkenyl Bromides by Brominative Deoxygenation of Ketones in One or Two Steps
作者:Ulrich Von Roman、Jakob Ruhdorfer、Rudolf Knorr
DOI:10.1055/s-1993-25986
日期:——
The conversion of ketones into alkenyl bromides is accomplished in one or two steps by 2,2,2-tribromo-2,2-dihydro-1,3,2-benzodioxaphosphole or by the dibromomethyl methyl ether prepared therefrom. Investigations of the scope and limitations provide some hints for the preparative planning and improvement.
A catalytic allylic cation-induced intermolecular allylation-semipinacol rearrangement
作者:Ming-Hui Xu、Kun-Long Dai、Yong-Qiang Tu、Xiao-Ming Zhang、Fu-Min Zhang、Shao-Hua Wang
DOI:10.1039/c8cc04285c
日期:——
A catalytic intermolecular semipinacol rearrangement induced by allylic carbocations has been realized. This tandem reaction is highly efficient under the catalysis of ZnBr2, generating a wide range of α-homoallyl substituted ketones which contain all-carbon quaternary centres in good to excellent yields (up to 98%) with moderate to high diastereoselectivities (up to >20 : 1). Synthetic application
sulfonylation/semipinacol rearrangements of allylic alcohols were developed using cheap and stable RSO2Na (R = CF3, Ph) as reagents. Various β-trifluoromethyl and sulfonated ketones were obtained in moderate to excellent yields. This strategy provides a facile, direct, and complementary approach to construct all-carbon quaternary stereocenters. In addition, the reaction has the advantages of being chemical oxidant-free
Electrophilic Trifluoromethylthiolation/Semipinacol Rearrangement: Preparation of β-SCF<sub>3</sub> Carbonyl Compounds with α-Quaternary Carbon Center
作者:Chao-Chao Xi、Zhi-Min Chen、Shu-Yu Zhang、Yong-Qiang Tu
DOI:10.1021/acs.orglett.8b01627
日期:2018.7.20
A new and modular electrophilic trifluoromethylthiolation/semipinacol rearrangement of allylic silyl ethers has been developed under mild conditions. This approach allows the formation of a number of β-SCF3 carbonyl compounds with a cyclic and all-carbon quaternary center framework in moderate to good yields. It should be noted that this achievement is a metal-free process and just requires the use
Metal-Free Transfer Hydrobromination of C–C Triple Bonds
作者:Weiqiang Chen、Martin Oestreich
DOI:10.1021/acs.orglett.9b01431
日期:2019.6.21
A transfer hydrobromination of C–C triplebonds inititated by Brønsted acids is reported. Hydrogen bromide is released stepwise from a bench-stable cyclohexa-1,4-diene-based surrogate, generating biphenyl and ethylene as waste. A range of vinyl bromides was prepared from terminal and internal, mainly acceptor-substituted alkynes with good functional-group tolerance.