Undecenyl resorc[4]arene in the chair conformation as preorganized synthon for olefin metathesis

Tetramerization of (E)-2,4-dimethoxycinnamic acid v-undecenyl ester with ethereal BF3 gave three stereoisomers 1a, 1b, and 1c, which were assigned as the chair, cone, and 1,2-alternate conformations, respectively. The chair conformation of 1a was confirmed by X-ray diffraction analysis, which also showed a peculiar self-assembly behavior in the crystal lattice, forming intercalated hydrophilic and hydrophobic layers (6-7 Å thickness) as a consequence of strong CH-p interactions. Undecenyl resorc[4]arene 1a, which featured the simplest pattern of substituents, was submitted to olefin metathesis using the second generation Grubbs complex as the catalyst. Depending on the reaction conditions, different products were isolated: a bicyclic alkene 2a (46%), a linear dimer 3a (5%), and a cross-linked homopolymer P1a (44%)