Catalytic cyclopropanation of polybutadienes

(Acetonitrile)[hydrotris(3,4,5-tribromo)-pyrazolylborate]copper, TpBr3Cu(NCMe)

“…14). 17 This was demonstrated for semicrystalline 1,2-polybutadiene as the starting material, resulting in side-chain functionalization, as well as with 1,4-cis-polybutadiene, resulting in main-chain substitution. In the same way, styrene-butadiene rubbers can be readily modified under mild conditions by the controlled, selective catalytic cyclopropanation of their double bonds.…”

Cyclopropanation of poly(isoprene) using NHC‐Cu(I) catalysts: Introducing carboxylates

“…The M n shows in general an increase after modification while the PDI essentially remains the same and is an indication that chain scission associated with many similar postpolymerization reactions did not appear. [19] The effect of the modification onto the glass transition temperature T g was investigated by DSC as it is of special importance for the desired tire application (see Table 3). There appears to be a reduction in the segmental mobility due to reduction in rotation around the CH 2 bonds in the backbone of the macromolecules, corresponding to the increase in the number of polar ester groups, [3,39] as the T g of the virgin PI 3shows an increase from −67 C to −61 C and − 58 C for 5% modified PI, cyclopropanated by EDA (4) and t-BDA (5), respectively.…”

“…[ 3 ] A more sophisticated approach used a [Tp Br3 Cu(NCMe)] catalyst (Tp Br3 = hydrotris[3,4,5‐tribromo‐1‐pyrazolyl]borate) in the presence of ethyl diazoacetate (EDA) to modify 1,2‐ and 1,4‐ cis ‐polybutadiene revealing 80% up to 100% functionalization of the corresponding double bonds. [ 19 ] However, the synthesis of the catalyst [Tp Br3 Cu(NCMe)] [ 20 ] proceeds via the highly toxic Tl[Tp Br3 ] thallium precursor. [ 21 ] Though the obtained results are remarkable, the scale‐up of the catalyst production is highly restrictive due to the toxicity of the thallium.…”

“…[ 10 ] To the best of our knowledge, no reports are published using NHC‐Cu(I) catalyzed cyclopropanation of poly(diene)s via diazoacetates, thus presenting the use of NHC‐Cu(I) complexes as an alternative to previously mentioned toxic or expensive transition metals. [ 19 ]…”

Understanding structure–property relationships of main chain cyclopropane in linear polyesters

“…19 Mecking and co-workers have demonstrated that an increase in the side chain cyclopropane content within polybutadiene led to a higher T g and a decrease in bulk crystallinity. 20 Whilst this effectively manipulated thermal properties, the focus was on side chain functionality. As a result of this, the architectural and stereochemical influence that could have resulted from main chain cyclopropane was not examined.…”