Synthesis of allenes via palladium-catalyzed hydrogen-transfer reactions: propargylic amines as an allenyl anion equivalent.
Synthesis of allenes has been achieved by using palladium-catalyzed hydrogen-transfer reactions. Various propargylic amines, which were readily prepapred from iodobenzenes and propargylic amines by Sonogashira coupling reaction, underwent the hydrogen-transfer reaction in the presence of Pd2dba3.CHCl3/(C6F5)3P catalyst at 100 degrees C in dioxane for 24 h, giving the corresponding allenes in 43-99% yields. Various propargylic alcohols containing a propargylic aminomethyl group, synthesized by the addition of lithium acetylides of N,N-diisopropylprop-2-ynylamine to aldehydes and a ketone, also underwent the hydrogen-transfer reaction in the presence of Pd2dba3.CHCl3 catalyst and (C6F5)3P at 80 degrees C in dioxane, giving the corresponding allenes in 56-92% yields. In the current transformation, propargylic amines can be handled as an allenyl anion equivalent and introduced into various electrophiles to be transformed into allenes under palladium-catalyzed conditions.
Nakamura
Hiroyuki
H
Department of Chemistry, Faculty of Science, Gakushuin University, Mejiro, Toshima-ku, Tokyo 171-8588, Japan. hiroyuki.nakamura@gakushuin.ac.jp
Kamakura
Takaya
T
Ishikura
Makoto
M
Biellmann
Jean-François
JF