NHC–gold(<scp>i</scp>) catalysed [4 + 2] cycloaddition–acyclic addition of dialkyl substituted propargylic esters with 1,3-diphenylisobenzofuran: synthesis of novel benzo[c]fluorenols and substituted dienes
作者:Ramesh Kotikalapudi、A. Leela Siva Kumari、K. C. Kumara Swamy
DOI:10.1039/c4ra01105h
日期:——
A gold carbene complex [IPrAuCl/AgSbF6] catalysed novel cycloaddition of propargylic esters with 1,3-diphenylisobenzofuran is reported. A [4 + 2] cycloaddition followed by sequential aromatic allylation leading to pentannulation with the expulsion of benzoic acid, then 1,2-phenyl migration coupled with ring opening and aromatisation leading to a new class of benzofluorenols, is discovered. This process
The mechanism of the catalysis of the reversible (propargyl ester)/(allenyl ester) rearrangement (10 ⇄ 11) by silver(I) ions was investigated, using optically active and diastereoisomeric esters as well as 14C- and 18O-labelling.
mediated by Pd(II) afforded cyclic orthoesters, which were hydrolyzed into γ-acetoxy-β-ketoesters. Based on the NMR experiments, it was presumed that the cyclization reaction was initiated by a nucleophilic attack of carbonyl oxygen to the alkyne carbon coordinated to palladium(II). When the γ-acetoxy-β-ketoesters were treated with a basic condition, Knoevenagel–Claisen type condensation took place, and