Synthesis and Stereospecific Polymerization of a Novel Bulky Styrene Derivative

Asymmetric Hydroarylation Reactions Catalyzed by Transition Metals: Last 10 Years in a Mini Review

Hydroarylation reactions play a pivotal role in organic chemistry due to their versatility and efficiency. In the last 10 years, the scientific production around this reaction has been very high, but in its asymmetric version, the results are less. In this mini review, selected literature examples are considered to draw attention to directions of the asymmetric hydroarylation reaction mediated by transition metal catalysts. The selected works were grouped in two main sections. In the first, we reported examples relating the narrower definition of hydroarylation, namely the metal-catalyzed processes where inactivated aryl moiety undergoes a direct functionalization via insertion of an unsaturated compound. In the second part, hydroarylation reactions take place with the use of pre-activated aryl substrates, usually aryl-iodides or aryl-boronated.

Isospecific Polymerization of Halide- and Amino-Substituted Styrenes Using a Bis(phenolate) Titanium Catalyst

Isospecific polymerization of polar styrenes is a challenge of polymer science. Particularly challenging are monomers bearing electron-withdrawing substituents or bulky substituents. Here, we report the coordination polymerization of halide- and amino-functionalized styrenes including para-fluorostyrene (pFS), para-chlorostyrene (pClS), para-bromostyrene (pBrS), and para-(N,N-diethylamino)styrene (DMAS) using 2,2′-sulfur-bridged bis(phenolate) titanium precursor (1). The combination of 1 and [Ph3C][B(C6F5)4] and AliBu3 provides crystalline poly(pFS)s with perfect isotacticity (mmmm > 95%) and high molecular weights (≤16.0 × 104 g mol−1). Upon activation with a large excess of DMAO, 1 reaches polymerization activity of 5.58 × 105 g molTi−1 h−1 producing isotactic poly(pFS)s featuring higher molecular weights (≤39.6 × 104 g mol−1). The distinguished performance of the 1/DMAO system has been extended to the polymerization of pClS and pBrS, both usually involve halogen abstraction during the polymerization, to produce isotactic and high molecular weight (Mn = 32.2 × 104 vs. 13.7 × 104 g mol−1) polymers in good activities (2.18 × 105 vs. 1.31 × 105 g molTi−1 h−1). Surprisingly, 1/DMAO is nearly inactive for DMAS polymerization, on contrary, the system 1/[Ph3C][B(C6F5)4]/AliBu3 displays isoselectivity (mmmm > 95%) albeit in a moderate activity.

Crystalline sulfur-functionalized poly(α-olefin) synthesized by scandium-catalyzed coordination polymerization

Combined with organoborate, the scandium complex catalyzed monomers to produce a series of syndiotactic sulfur-functionalized poly(α-olefin)s (rrrr of up to 0.95) which formed crystalline materials with a Tm of up to 91 °C.

Syndiospecific coordination (Co)polymerization of carbazole-substituted styrene derivatives using the scandium catalyst system

Perfect syndiospecific polymerization of carbazole-substituted styrene derivatives was achieved using a rare-earth metal catalyst. Also copolymerization of FSt with styrene afforded copolymers with gradient sequence distributions and easily tunable incorporation rate.

Low-Symmetry β-Diketimine Aryloxide Rare-Earth Complexes: Flexible, Reactive, and Selective

We report the synthesis, characterization, and reactivity of a new low-symmetry β-diketimine featuring a pendant amino(methyl)phenol donor and its corresponding heteroleptic rare-earth (RE) complexes. This includes the first structurally characterized examples of alcoholysis and insertion from an isolated RE^III amide in a β-diketimine framework. The flexible methylene linkage leads to RE^III complexes with tunable dynamic solution behavior that defines their stoichiometric and catalytic reactivity. The addition of a strong neutral donor ligand, tricyclohexylphosphine oxide, suppresses a prevalent catalyst degradation pathway (base-promoted elimination) and dramatically enhances the catalyst performance in the stereospecific ring-opening polymerization of rac-β-butyrolactone. Our results further demonstrate the importance of ligand reorganization in the stoichiometric and catalytic activity of RE^III ions.

Enantioselective Preparation of Arenes with β-Stereogenic Centers: Confronting the 1,1-Disubstituted Olefin Problem Using CuH/Pd Cooperative Catalysis

Arenes with β-stereogenic centers are important substructures in pharmaceuticals and natural products. We have developed an asymmetric anti-Markovnikov hydroarylation of 1,1-disubstituted olefins by dual palladium and copper hydride catalysis as a convenient and general approach to access these substructures. This efficient one-step process addresses several limitations of the traditional stepwise approaches. The use of cesium benzoate as a base and a common phosphine ligand for both the Cu- and Pd-catalyzed processes were important discoveries that allow these challenging olefin substrates to be efficiently transformed. A variety of aryl bromide coupling partners, including numerous heterocycles, were coupled with 1,1-disubstituted alkenes to generate arenes with β-stereogenic centers.

Self-assembly and fluorescence emission of UV-responsive azobenzene-containing helical poly(phenyl isocyanide) copolymers

UV-responsive azobenzene-containing helical copolymers were obtained, and their self-assembly and fluorescent properties were investigated.

Effect of the tactic structure on the chiroptical properties of helical vinylbiphenyl polymers

The effect of a tactic structure on the chiroptical properties of helical vinylbiphenyl polymers is systematically studied.

Convenient synthesis of versatile syndiotactic polystyrene materials containing pendant alkenyl groups with a scandium catalyst system

The syndioselective copolymerization of styrene with five alkenyl functionalized styrenic monomers, with the use of a scandium catalyst, produced a new family of versatile syndiotactic polystyrene materials with pendant alkenyl groups.

Highly syndioselective coordination (co)polymerization of isopropenylstyrene

Coordination (co)polymerization of para-isopropenylstyrene (pIPSt) and meta-isopropenylstyrene (mIPSt), initiated by scandium (Sc) based catalysts, afforded new type of products, bearing pendant isopropenyl groups with perfect syndiotacity (rrrr > 99%).

Gradient helical copolymers: synthesis, chiroptical properties, thermotropic liquid crystallinity, and self-assembly in selective organic solvents

A series of novel gradient copolymers R-(−)-poly(StN-grad-C8) were synthesized through atom transfer radical copolymerization of an achiral styrenic monomer, N,N-dimethyl-4-ethenylbenzamide (M-StN), and a chiral bulky vinylterphenyl monomer, (−)-2,5-bis{4′-[(R)-sec-octyloxycarbonyl]phenyl}styrene (R-(−)-M-C8).

Facile synthesis and chiral recognition of block and star copolymers containing stereoregular helical poly(phenyl isocyanide) and polyethylene glycol blocks

A new Pd(ii) initiator bearing an alkyne headgroup was designed and synthesized.

A facile synthetic route to stereoregular helical poly(phenyl isocyanide)s with defined pendants and controlled helicity

A facile synthetic route to stereoregular helical poly(phenyl isocyanide)s with not only defined pendants but also with controlled helicity was developed.