Cp(π-Allyl)Pd-Initiated Polymerization of Diazoacetates: Reaction Development, Kinetic Study, and Chain Transfer with Alcohols

Abstract

A new initiating system, (cyclopentadienyl) (π-allyl)­palladium­(II) [Cp­(π-allyl)­Pd], for the polymerization of diazoacetate monomers has been developed. Homo- and copolymers bearing an ester substituent at every main-chain carbon atom were efficiently synthesized from various alkyl and aryl diazoacetates. In particular, this polymerization system can tolerate various functional groups, which allows for effective postpolymerization functionalization of the resultant polymers. Detailed kinetic study indicates that this polymerization has the characteristics of slow initiation and rapid propagation. Furthermore, alcohols were found to function as chain transfer agents as confirmed by polymerization experiments and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analyses of the polymer products, thus providing an effective method for controlling the molecular weight of the polymer.

Polymerization of Diazoacetates Initiated by the Pd(N-arylmaleimide)/NaBPh4 System: Maleimide Insertion into a Pd–C Bond Preceding to Initiation Leading to Efficient α-Chain-End Functionalization of Poly(alkoxycarbonylmethylene)s

“…Further, Toste and co-workers found that π-allylPd­(carboxylate) dimers, in which the chloride on (π-allylPdCl) 2 was replaced with more nucleophilic carboxylates, can initiate polymerization of some diazoacetates in a controlled manner to give PACMs with low dispersity . In addition, Wang and co-workers demonstrated that π-allylPdCp (Cp = cyclopentadienyl) can polymerize various diazoacetates efficiently to give PACMs in good yield …”

Polymerization with the Cu(i)-catalyzed Doyle–Kirmse reaction of bis(allyl sulfides) and bis(α-diazoesters)

“…C1 polymerization of diazo compounds affords polymers bearing polar substituents on every main-chain carbon atom, which are difficult to synthesize by traditional vinyl addition polymerizations. 3,4 In addition, diazo compounds have also been used in step-growth polycondensations, including O–H 5 and N–H 6 insertions, CC bond formations 7 and carbene-based cross-coupling reactions 8 (Scheme 1a and b). However, other typical reactions of diazo compounds, such as cyclopropanation and ylide generation/rearrangement, have not been explored in polymerization.…”

Diazoacetates as Terminating Agents in Living Ring-Opening Metathesis Polymerization: Synthesis of Chain-End-Functionalized Polymers

“…As part of our continuous interests in diazo compounds both in organic and polymer chemistry, − we are thus interested in whether the high reactivity of diazo compounds could be harnessed to allow for efficient capping of ruthenium carbenes at polymer chain ends under suitable, mild conditions, which open doors to a new category of terminating agents beyond unsaturated carbon–carbon bonds. Herein, we report the utilization of diazoacetates as a new type of terminating and end-functionalizing agents for ruthenium-catalyzed ROMP (Scheme c).…”