Elliott H. Denton

We report the reversible deactivation radical copolymerization of bioderived α‐methylene‐δ‐valerolactone (MVL) with methacrylate, styrenic, and acrylate comonomers using reversible addition–fragmentation chain transfer (RAFT) and photo‐induced atom transfer radical polymerization (photoATRP). Under optimized conditions, MVL was incorporated preferentially relative to the comonomer, giving well‐defined copolymers across a broad molecular‐weight range with low dispersity and enabling block‐copolymer synthesis by chain extension. Increasing MVL incorporation increased glass transition temperature across all monomers studied, consistent with the rigid pendant lactone unit. These results establish MVL as a practical bio‐derived comonomer for reversible deactivation radical polymerization and as a route to functional vinyl copolymers with enhanced thermal performance.

Phosphinephenol esters react with Ni⁰ to afford otherwise difficult to access Ni^II-alkyl complexes. The reaction proceeds efficiently and cleanly by coordination of phosphine to the Ni⁰, which directs an intramolecular oxidative addition into the C(acyl)-O bond followed by rapid carbon monoxide elimination. The potential of this mild preparative pathway was demonstrated by the synthesis of a higher Ni^II-n-alkyl complex, and of a five-membered chelate that is the key intermediate in the nonalternating copolymerization of ethylene and carbon monoxide, as well as its ¹³C-labeled analog. Further, the title reaction can regenerate active polymerization catalyst after CO-induced deactivation under pressure reactor conditions, highlighting its broader utility. This shows the directed oxidative addition-decarbonylation of phenolesters provides a broad platform to access catalytically relevant Ni alkyl complexes.

Polymers containing cleavable functionality along the backbone represent a path to reduce the environmental persistence of commodity rubbers and plastics. One route to installing cleavable functionality involves the radical ring-opening polymerization of five-membered 1,2-dithiolanes such as α-lipoic acid, which introduces disulfide bonds into vinyl polymer backbones. However, the ring strain and electronics of 1,2-dithiolanes generally restrict reactivity to only favor copolymerization with more-activated comonomers, such as acrylate and styrene derivatives. Here, we show that the six-membered cyclic disulfide, 1,2-dithiane overcomes this limitation under simple thermal free-radical conditions. We demonstrate that 1,2-dithiane copolymerizes efficiently with the less-activated monomer vinyl acetate. In sharp contrast to α-lipoic acid and its derivatives, 1,2-dithiane exhibits nearly ideal copolymerization across different feed ratios, affording high conversions of both monomers (>90%), tunable molar masses (M_n ≈ 10-100 kg mol^-1), and scalability (>20 g). Moreover, the 1,2-dithiane scaffold is synthetically versatile: a 1,2-dithiane-4,5-diol was synthesized from dithiothreitol as a building block for further derivatization. By varying dithiane functionality and loading, poly(dithiane-co-vinyl acetate) copolymers span semicrystalline to elastomeric mechanical properties and, critically, embed backbone-cleavable sulfur motifs (including monothioacetal units) even at low (<1 mol %) loadings. This operationally simple reaction highlights the key influence of ring size in the copolymerization behavior of disulfide-containing monomers and demonstrates the practical advantages of using 6-membered cyclic disulfides as renewable building blocks for creating degradable vinyl copolymers derived from inexpensive, industrially relevant feedstocks.

Herein, we demonstrate that ligand design enables the direct addition of acid chlorides across alkynes in a single step with complete atom economy to afford α,β-unsaturated acid chloride products. This carbochlorocarbonylation reaction, which proceeds through the formal cleavage and reassembly of C-COCl bonds, was developed and explored for a range of acid chlorides and alkynes. During the course of this work, the formation of synthetically useful cyclopentenones through a formal C-H functionalization step was serendipitously observed at elevated temperatures. After optimizing for this divergent reactivity, we explored the substrate scope and undertook experiments to investigate the underlying mechanistic pathway for the formation of this product. Overall, this work expands the carbochlorocarbonylation reaction from activated substrates to alkynes. Further, it provides insight into ligand design for the exploration of fundamental reactivity.

The power and ability of catalysis to build multiple C−C bonds in a single step has had a transformative impact on organic synthesis. While the reactivity of organohalides with metal catalysts is widely appreciated, the related and more intricate reactivity of acid chlorides is less so, despite their use as common reagents in synthesis. Here, we review the transformations of acid chlorides in combination with unsaturated C−C bonds catalyzed by palladium, rhodium, or iridium and provide an outlook for future research opportunities.

A strategy for the palladium-catalyzed intermolecular synthesis of polysubstituted cyclopentenones is reported. The three-component reaction utilizes vinyl iodides and internal alkynes to form the carbon framework of the cyclopentenone with Cr(CO)₆ serving as an easy to handle, solid CO surrogate, and a hydrosilane as a hydride source. We demonstrate the scope of the reaction which includes a wide range of functional groups. The reaction is regioselective, with the use of linear or branched vinyl iodides resulting in the α- or β-substituted cyclopentenones, respectively. Further, we show that a two-step sequence from commercially available alkynes can be used to generate cyclopentenone products via formation of the vinyl iodide and subsequent Pauson-Khand-type reaction.