Marion Helou

Poly(carbonate-urethane): an isocyanate-free procedure from α,ω-di(cyclic carbonate) telechelic poly(trimethylene carbonate)s

A simple isocyanate-free method to synthesize poly(trimethylene carbonate hydroxy-urethane)s is described. The strategy first involves the synthesis of α,ω-di(cyclic carbonate) telechelic polycarbonate precursors upon ring-opening polymerization of trimethylene carbonate using a cyclic carbonate alcohol as chain transfer agent, followed by the ring-opening polyaddition of the terminal cyclic carbonate with a diamine. Such poly(carbonate-hydroxyurethane)s exhibit macromolecular carbonate segments of tunable length/molar mass.

Metal Triflates as Highly Stable and Active Catalysts for the “Immortal” Ring‐Opening Polymerization of Trimethylene Carbonate

The controlled “immortal” ring‐opening polymerization of trimethylene carbonate (TMC) using a two‐component catalyst system based on a metal Lewis acid, such as a metal triflate M(OTf)n (M=Ca, Sc, Zn, Al, Bi; OTf=CF3SO3−) or the metallic salt Fe(acac)3, (acac=acetylacetonate) and an alcohol (ROH) as co‐initiator and chain‐transfer agent, is carried out in bulk at 110–150 °C. As a result of the water‐tolerance of these systems, experimental operating conditions do not require any special care. The approach, valorized both with various ROH transfer agents and with either purified or unpurified monomer sources, is highly versatile. Functional telechelic polycarbonates HPTMCOR, devoid of decarboxylation sequences, are obtained [PTMC=poly(trimethylene carbonate)]. The molar mass of the PTMCs can be readily predicted by a simple model, taking into account the [TMC]0/[ROH]0 ratio and the amount of transferring impurities present in the raw/unpurified reagents. Such simple, air‐ and moisture‐robust catalytic systems, which display quite high activities (TOF up to 28 200 h−1) and productivities (TON up to 45 000) are thus extremely valuable, especially industrially. The performances of these systems are described in comparison to the previously established valuable inorganic and organometallic catalytic systems, namely metal amido complexes ([M{N(SiMe3)2}3]) and [(BDI)Zn{N(SiMe3)2}] (BDI=β‐diiminate ligand) derivatives.

Ruthenium-Catalyzed Synthesis of Allylic Alcohols : Boronic Acid as a Hydroxide Source

Secondary allylic alcohols were synthesized from linear allylic halides or carbonates using a catalytic amount of a ruthenium complex in the presence of boronic acid. The effects of solvent, base, ruthenium precursor, and boronic acid were fully explored, and the scope of the reaction was extended to various substrates. We also describe a preliminary investigation towards an enantioselective process.

Functionalized polycarbonates from dihydroxyacetone: insights into the immortal ring-opening polymerization of 2,2-dimethoxytrimethylene carbonate

Functionalized polycarbonates derived from 2,2-dimethoxytrimethylene carbonate (TMC(OMe)2) have been prepared with controlled molecular features by immortal ring-opening polymerization, under mild conditions (bulk, 60–90 °C), using various (metallo)organic/alcohol (diol) binary catalyst systems: the β-diiminate zinc complex [(BDIiPr)Zn(N(SiMe3)2)] (BDI = CH(CMeNC6H3-2,6-iPr2)2), the aluminium triflate, or the organic bases 4-N,N-dimethylaminopyridine (DMAP), 1.5.7-triazabicyclo-[4.4.0]dec-5-ene (TBD) and 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP), as catalyst precursors, combined with benzyl alcohol or 1,3-propanediol acting both as a co-initiator and a chain transfer agent. For the first time, well-defined α-hydroxy-ω-alkoxyester and α,ω-dihydroxy telechelic acetal-functionalized homopolycarbonates were thus prepared with molar mass up to 70 200 g mol−1. These polymers were characterized at the molecular (NMR, SEC), thermal (DSC, TGA) and mechanical levels, and compared to conventional PTMC. P(TMC(OMe)2) is a rigid and brittle polymer material (E = 3190 ± 70 MPa, er = 9 ± 1%).

Metal catalyzed ring-opening polymerization of benzyl malolactonate: a synthetic access to copolymers of β-benzyl malolactonate and trimethylene carbonate

The “immortal” coordination–insertion ring-opening polymerization of benzyl malolactonate (MLABe) initiated by the two-component catalyst system based on the zinc amide precursor, (BDI)Zn[N(SiMe3)2] (BDI = β-diiminate ligand), and benzyl alcohol (BnOH) acting as a co-initiator and a chain transfer agent proceeds in bulk at 40 °C. Functional telechelic poly(β-benzyl malolactonate)s, H-PMLABe-OBn, are thus obtained. Sequential copolymerization with trimethylene carbonate (TMC) affords block copolymers, PTMC-b-PMLABe, which are alternatively prepared from the chemical coupling of the PMLABe-COOH and PTMC-OH homopolymers. Simultaneous copolymerization of both the lactone and the carbonate monomers offers the PTMC-co-PMLABe random copolymers. The (co)polymers have been characterized by NMR, FT-IR, SEC and DSC analyses. These represent the first examples of β-benzyl malolactonate/carbonate copolymers. More importantly, these (co)polymers could be synthesized free of metallic residues thereby making them suitable as biomedical and pharmaceutical biomaterials.

Ethylene carbonate/cyclic ester random copolymers synthesized by ring-opening polymerization

The diaminophenolate and β-diketiminate zinc complexes [(NNO)ZnEt] ((NNO)− = 2,4-di-tert-butyl-6-{[(2′-dimethylaminoethyl)-methylamino]methyl}phenolate)) and [(BDIiPr)Zn{N(SiMe3)2}] (BDIiPr = CH(CMeNC6H3-2,6-iPr2)2), respectively, the Lewis acidic triflate salt Al(OTf)3, and the guanidine TBD (= 1,5,7-triazabicyclo[4.4.0]dec-5-ene), combined to a protic source as initiator, typically benzyl alcohol (BnOH), enabled the successful copolymerization of ethylene carbonate (EC) with various cyclic esters such as β-butyrolactone (BL), δ-valerolactone (VL), e-caprolactone (CL) or L-lactide (LLA). The random copolymerizations proceeded smoothly under mild operating conditions, preferentially from [(NNO)ZnEt]/BnOH at 60 °C in toluene within a few hours, affording the corresponding copolymers void of ether units, with Mn,SEC values in the range ca. 6000–93 350 g mol−1 and with unimodal, moderately broad dispersity values (ĐM = 1.3–2.1). Under the same experimental conditions, the homopolymerization of EC did not proceed. The first EC/BL random copolymers were thus synthesized with up to 26 mol% of EC inserted within the polyester, while the second example of P(EC-co-VL) was isolated. P(EC-co-VL), P(EC-co-CL), and P(EC-co-LLA) copolymers were prepared with higher than previously reported EC content, namely 23, 37, and 17 mol% vs. 10, 31, and 4 mol%, respectively. In contrast to other catalyst systems, the Al(OTf)3/BnOH system promoted CO2 elimination from the copolymers, thereby leading to ether defects. Microstructural analysis of the copolymers by 13C{1H} NMR spectroscopy revealed the presence of signals previously never described and possibly arising from consecutive EC units within the random copolymers. Thermal transition temperatures measured by DSC further supported the random nature of these copolymers.

Ruthenium-catalyzed tandem allylic substitution/isomerization: a direct route to propiophenones from cinnamyl chloride derivatives

A tandem nucleophilicsubstitution/redox isomerization catalyzed by a single ruthenium catalyst leads to the direct transformation of allylic chlorides into propiophenones.