101321-34-0Relevant academic research and scientific papers
Discovery of a Photoinduced Dark Catalytic Cycle Using in Situ LED-NMR Spectroscopy
Lehnherr, Dan,Ji, Yining,Neel, Andrew J.,Cohen, Ryan D.,Brunskill, Andrew P. J.,Yang, Junyu,Reibarkh, Mikhail
supporting information, p. 13843 - 13853 (2018/10/24)
We report the use of LED-NMR spectroscopy to study the reaction mechanism of a newly discovered photoinduced iron-catalyzed cycloisomerization of alkynols to cyclic enol ethers. By understanding on/off ligand binding to the catalyst, we were able to appro
Intramolecular hydroalkoxylation/cyclization of alkynyl alcohols mediated by lanthanide catalysts. Scope and reaction mechanism
Seo, SungYong,Yu, Xianghua,Marks, Tobin J.
supporting information; experimental part, p. 263 - 276 (2009/06/28)
Lanthanide-organic complexes of the general type Ln[N(SiMe 3)2]3 (Ln = La, Sm, Y, Lu) serve as effective precatalysts for the rapid, exoselective, and highly regioselective intramolecular hydroalkoxy- lation/cyclization of primary and secondary alkynyl alcohols to yield the corresponding exocyclic enol ethers. Conversions arehighly selective with products distinctly different from those generall y produced by conventional transition metal catalysts, and turnover frequencies as high as 52.8 h-1 at 25 °C are observed. The rates of terminal alkynl alcohol hydroalkoxylation/cyclization are significantly more rapid than those of internal alkynyl alcohols, arguing that steric demands dominate the cyclization transition state. The hydroalkoxylation/cyclization of internal alkynyl alcohols affords excellent E -selectivity. The hydroalkoxylation/ cyclization of the SiMe3-terminated internal alkynyl alcohols reveals interesting product profiles which include the desired exocyclic ether, a SiMe3-eliminatedexocyclic ether, and the SiMe3-O- functionalized substrate. The rate law for alkynyl alcohol hydroalkoxylation/ cyclization is first -order in [catalyst] and zero-order in [alkynyl alcohol], as observed inthe intramolecular hydroamination/cyclization of aminoalkenes, aminoalk ynes, and aminoallenes. An ROH/ROD kinetic isotope effect of 0.95(0.03) is observed for hydroalkoxy- lation/cyclization. These mechanistic data implicate turnover-limiting insertion of C-C unsaturation into the Ln-O bond, involving a highly organized transition state, with subsequent, rapid Ln-C protonolysis.
