posted on 2024-01-04, 14:06authored byShijia Li, Qiang Feng, Lijuan Song, Xinhao Zhang, Yun-Dong Wu, Jianwei Sun
Described here is a mild and stereoselective
protocol for the synthesis
of [3]dendralenes via the intermolecular dimerization of allenes.
With the proper choice of a ruthenium catalyst, a range of unactivated
1,1-disubstituted allenes, without prefunctionalization in the allylic
position, reacted efficiently to provide rapid access to densely substituted
[3]dendralenes. An intermolecular C–C bond and three different
types of CC double bonds (di-, tri-, and tetrasubstituted)
embedded in an acyclic structure were constructed with good to high E/Z stereocontrol. This is in contrast
to the known catalytic protocols that focus on allenes with prefunctionalization
at the allylic position and/or monosubstituted allenes, which would
proceed by a different mechanism or require less stereocontrol. The
silyl-substituted dendralene products are precursors of other useful
dendralene molecules. Density functional theory (DFT) studies and
control experiments supported a mechanism involving oxidative cyclometalation,
β-H elimination (the rate-determining step), and reductive elimination.