New Monomers and Polymers from Plant Oils via Thiol-ene Additions

We recently reported on the synthesis of different chain length α,ω-diester monomers from plant oil derived fatty acid esters or fatty alcohols via olefin cross-metathesis with methyl acrylate taking advantage of natures "synthetic pool" of fatty acids with different chain lengths and positions of double bonds. [1,2,3] Similarly, we could show that their cross-metathesis with allyl chloride allows for the synthesis of α,ω-difunctional compounds. [3] Therefore, this strategy offers the possibility to introduce a variety of functional groups to the ω-position of fatty acid derivatives, thus providing valuable starting materials for a variety of polyesters and polyamides. Within this contribution, a complementary approach towards renewable monomers and polymers utilizing thiol-ene click chemistry will be introduced and discussed. [5] Also this approach takes advantage of the inherent double bond functionality of fatty acids and their derivatives and allows introducing a large variety of functional groups to fatty compounds. For instance, the castor oil derived methyl 10-undecenoate [6] was used to prepare a set of monomers with high yields in an environmentally friendly reaction (no solvent, low E-factors). These monomers were subsequently polymerized to yield renewable polyesters, the material properties of which will be discussed within this contribution. Moreover, thiol-ene click chemistry was used to polymerize fatty acid derived monomers and renewable plant oil derived dendrimers were prepared via this approach. In summary, thiol-ene addition reactions are as versatile as olefin metathesis for the introduction of functional groups in an efficient and environmentally friendly manner in the field of oleochemistry. [7]