Gold-Catalyzed Formation of Oxonium Ions from Enynes and Their Intra- and Intermolecular Trapping with Allylsilanes
作者:Jingwei Li、Xiaoguang Liu、Daesung Lee
DOI:10.1021/ol203206k
日期:2012.1.6
Gold-catalyzed ringclosure of 1,5-enyne containing a silyl ether at the allylic position induces a skeletal rearrangement to form an oxonium intermediate, which then undergoes a smooth allylation in both an intra- and intermolecular manner. In the intramolecularallyltransfer, the additive alcohol becomes positioned on the silicon of the silyl ether by forming a new Si–OR bond, whereas, in the intermolecular
Facile hydrogen/metal exchange between butylpotassium and saturated ethers
作者:Ruth Lehmann、Manfred Schlosser
DOI:10.1016/s0040-4039(01)80015-0
日期:1984.1
At temperatures between −100 and −40°C, lithium salt-free butylpotassium (prepared from dibutylmercury) readily metalates saturated ethers such as dimethyl ether or tetrahydrofuran.
2-oxonia Cope rearrangement is shown to play an important role in Lewis acid-induced π-cyclization reactions of a variety of methyl 2-acetoxy-2-(3-alken-1-oxy)acetates to 5- and 6-membered ring ethers. The influence of this [3,3]-sigmatropic rearrangement on the regio- and stereochemical outcome of the cyclization is evaluated by studying three types of substrates, namely (1) four chain-substituted precursors
Synthesis of γ,δ,-unsaturated α-amino acids from allylsilanes and glycidyl cation equivalents
作者:Hendrik H. Mooiweer、Henk Hiemstra、W.Nico Speckamp
DOI:10.1016/s0040-4020(01)89098-0
日期:——
The synthesis of a series of γ,δ-unsaturated N-protected α-amino acid methyl esters from the coupling of different allylsilanes and glycidyl cation equivalents 6 and 7 is described. Reactions with methoxyglycine derivative 6 are induced with BF3·OEt2; in the case of chloroglycine derivative 7 SnCl4 is used as Lewis acid. Reactions are fully regioselective, but show low stereoselectivity. The conversion
β-Trimethylsilyl allenes have been prepared in fair to good yields fromallylsilanes by successive dibromocarbene addition and rearrangement of the cyclopropylidenes. In the case of 3,6-bis(trimethylsilyl)cyclohexa-1,4-diene, insertion of dibromocarbene occurs in the silicon-carbon bond leading to α-bromobenzyltrimethylsilane.