Addition of heteroaromatics to alkylidenecyclopropanes catalyzed by palladium.
The reaction of heteroaromatics, such as furans, thiophenes, thiazoles, and pyrroles, with alkylidenecyclopropanes proceeded smoothly in the presence of palladium catalysts, producing the corresponding alpha-allylated products in good to high yields. For example, the reaction of 3-butylpentylidenecyclopropane (1a) with 2-methylfuran (2a), ethyl 2-thiophenecarboxylate (4a), 2-isobutylthiazole (6a), and 1-methylpyrrole (11b) gave the alpha-allylated products in 70%, 66%, 77%, and 30% yield, respectively. The reaction proceeded predominantly through distal bond cleavage. The order of reactivity of heteroaromatics toward 1a is as follows: furan > thiophene approximately thiazole (5-position) > thiazole (2-position) approximately pyrrole. This methodology provides a means for introducing an allylic group to various kinds of heteroaromatics under mild conditions.
Nakamura
Itaru
I
Department of Chemistry, Graduate School of Science, and Research Center for Organic Resources and Material Chemistry, Institute for Chemical Reaction Science, Tohoku University, Sendai 980-8578, Japan.
Siriwardana
Amal I
AI
Saito
Shinichi
S
Yamamoto
Yoshinori
Y