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Cationic P(OPh) 3 ‐ or PPh 3 ‐Rhodium(I) Complex‐Catalyzed Isomerizations of 5‐Alkynals to δ‐Alkynyl Ketones, Cyclopent‐1‐enyl Ketones, and Cyclohexenones
Author(s) -
Tanaka Ken,
Sasaki Kaori,
Takeishi Kenzo,
Hirano Masao
Publication year - 2007
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200700550
Subject(s) - chemistry , isomerization , catalysis , rhodium , cationic polymerization , hydroacylation , medicinal chemistry , ketone , stereochemistry , organic chemistry
We have developed catalytic isomerizations of 5‐alkynals to γ‐alkynyl ketones and cyclopent‐1‐enyl ketones using [Rh{P(OPh) 3 } 2 ]BF 4 as a catalyst. Cu(OTf) 2 and AgBF 4 are also effective catalysts for the formation of γ‐alkynyl ketones. The substituents at the 4‐positions in 5‐alkynals play important roles in the selection of two different isomerization pathways. The first catalytic endo / trans hydroacylation of acyclic 5‐alkynals leading to cyclohexenones was also developed with [Rh(PPh 3 ) 2 ]BF 4 as a catalyst. Crossover deuterium‐labeling studies indicated that these isomerization reactions proceed intramolecularly.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)