A Novel, Short and Repeatable Two-Carbon Ring Expansion Reaction by Thermo-Isomerization: Easy Synthesis of Macrocyclic Ketones
作者:Matthias Nagel、Hans-Jürgen Hansen、Georg Fráter
DOI:10.1055/s-2002-19758
日期:——
A novel two-carbon ring enlargement procedure, in which medium- and large-ring 1-vinylcycloalkanols are thermoisomerized in a flow reactor system at temperatures of 600 °C to about 650 °C, produces the isomeric ring-expanded cycloalkanones directly and efficiently. This two-step ringexpansion protocol can easily be applied several times successively. For e.g., the musk odorant cyclopentadecanone (Exaltone
Platinum catalysed hydrosilylation of propargylic alcohols
作者:Catherine A. McAdam、Mark G. McLaughlin、Adam J. S. Johnston、Jun Chen、Magnus W. Walter、Matthew J. Cook
DOI:10.1039/c3ob40496j
日期:——
A facile and user-friendly protocol has been developed for the selective synthesis of E-vinyl silanes derived from propargylicalcohols using a PtCl2/XPhos catalyst system. The reaction is generally high yielding and provides a single regioisomer at the β-position with E-alkene geometry. The reaction is extremely tolerant of functionality and has a wide scope of reactivity both in terms of alkynes
The first general and regioselective Pd‐catalyzed cyclocarbonylation to give α‐methylene‐β‐lactones is reported. Key to the success for this process is the use of a specific sterically demanding phosphine ligand based on N‐arylated imidazole (L11) in the presence of Pd(MeCN)2Cl2 as pre‐catalyst. A variety of easily available alkynols provide under additive‐free conditions the corresponding α‐methylene‐β‐lactones
Formal Alkylation of Allenes through Highly Selective Radical Cyclizations of Allene-enes
作者:Rong Zeng、Chunling Fu、Shengming Ma
DOI:10.1002/anie.201107747
日期:2012.4.16
example of alkene‐to‐allene radical cyclization of allene‐enes is reported. The highly chemoselective intermolecular radical addition reaction of the alkene and subsequent, exclusive exo‐radical addition to the allene was realized with perfluoroalkyl radicals (see scheme). A subsequent TBAF‐promoted dehydroiodination of the cyclization products forms cyclopentanes and regenerates an allene moiety (TBAF=t