Depolymerization of 1,4-polybutadiene by metathesis: high yield of large macrocyclic oligo(butadiene)s by ligand selectivity control

Abstract

Herein, we demonstrate a practical high yield preparation of large macrocyclic oligo(butadiene)s, preferably the C16 to C44 fraction, from commercial 1,4-polybutadiene by exploring intramolecular backbiting using a series of commercially available Ru catalysts.

Unprecedented Selectivity of Ruthenium Iodide Benzylidenes in Olefin Metathesis Reactions

“…Depolymerization of the widely used industrial polymer cis-1,4-polybutadiene (PBD) by olefin metathesis is a well-studied reaction that usually produces cyclic alkenes. [14] As expected for a non-terminal olefin, no reaction occurred when Ru-S-I was added to a PBD solution in hot toluene. However, if a small amount of DEDAM was also added, depolymerization readily took place.…”

Total Synthesis of (−)‐Cannabidiol‐C4

“…Treating acid 4 with 2.5 equivalents of methyl lithium (MeLi) yielded the corresponding ketone 13 in 78 % yield, which was subjected to the RCM (Scheme 3). Two types of catalysts were used to perform the reaction: Grubb's 2 nd generation (79 % yield) and Umicore M73 SIMes [25,26] (90 % yield). The latter resulted to be more efficient in terms of yield and purification, therefore it was selected as the best catalyst to achieve the desired product 3.…”

Selectively Depolymerizable Polyurethanes from Unsaturated Polyols Cleavable by Olefin Metathesis

“…Olefin metathesis is an attractive route to depolymerization of unsaturated rubbers, critically enabled by the nuanced chain microstructure (1,4‐ and 1,2‐addition products) characteristic of polydienes. [ 45–64 ] Adjacent double bonds in side‐ and main‐chain configurations are ring‐closed by Ru carbenes (Grubbs’ catalysts) to cyclopentene and cyclohexene species with concomitant cleavage of the polymer chain. [ 48,57,64 ] The further realization that cyclopentene, functionalized cyclopentenes, and other five‐membered alkene rings can be ring‐opened through judicious selection of reaction conditions has spawned recent development of polypentenamer elastomers and related materials, including networks with continuous recyclability through sequential ring‐opening and ring‐closing metathesis.…”

“…[ 45–64 ] Adjacent double bonds in side‐ and main‐chain configurations are ring‐closed by Ru carbenes (Grubbs’ catalysts) to cyclopentene and cyclohexene species with concomitant cleavage of the polymer chain. [ 48,57,64 ] The further realization that cyclopentene, functionalized cyclopentenes, and other five‐membered alkene rings can be ring‐opened through judicious selection of reaction conditions has spawned recent development of polypentenamer elastomers and related materials, including networks with continuous recyclability through sequential ring‐opening and ring‐closing metathesis. [ 65–72 ] Inspired by this general motif, we report here a series of novel PUs derived from carefully designed, unsaturated polyols, enabling facile depolymerization of the PUs by olefin metathesis.…”