Sensory Polymers: Trends, Challenges, and Prospects Ahead.

In recent years, sensory polymers have evolved significantly, emerging as versatile and cost-effective materials valued for their flexibility and lightweight nature. These polymers have transformed into sophisticated, active systems capable of precise detection and interaction, driving innovation across various domains, including smart materials, biomedical diagnostics, environmental monitoring, and industrial safety. Their unique responsiveness to specific stimuli has sparked considerable interest and exploration in numerous applications. However, along with these advancements, notable challenges need to be addressed. Issues such as wearable technology integration, biocompatibility, selectivity and sensitivity enhancement, stability and reliability improvement, signal processing optimization, IoT integration, and data analysis pose significant hurdles. When considered collectively, these challenges present formidable barriers to the commercial viability of sensory polymer-based technologies. Addressing these challenges requires a multifaceted approach encompassing technological innovation, regulatory compliance, market analysis, and commercialization strategies. Successfully navigating these complexities is essential for unlocking the full potential of sensory polymers and ensuring their widespread adoption and impact across industries, while also providing guidance to the scientific community to focus their research on the challenges of polymeric sensors and to understand the future prospects where research efforts need to be directed.

Gold(I) Catalysis Applied to the Stereoselective Synthesis of Indeno[2,1-b]thiochromene Derivatives and Seleno Analogues.

A gold(I)-catalyzed cascade reaction for the stereoselective synthesis of sulfur- or selenium-containing indeno[1,2-b]chromene derivatives from o-(alkynyl)styrenes substituted at the triple bond with a thio- or seleno-aryl group is described. The reaction involves a double cyclization process through a proposed key gold-cyclopropyl carbene intermediate that evolves by the intramolecular addition of an aromatic to the cyclopropane ring, affording polycyclic structures. The enantioselective version was studied using gold(I) complexes bearing chiral ligands.

Transition Metal-Free Synthesis of Halobenzo[b]furans from O-Aryl Carbamates via o-Lithiation Reactions.

A straightforward and transition metal-free one-pot protocol to synthesize halobenzo[b]furans has been developed employing simple and easily available starting materials such as O-aryl carbamates and alkynylsulfones. The fine-tuning of the different steps involved was key to achieving a successful one-pot procedure. Initially, a directed ortho-lithiation process, which uses the carbamate as the directed metalation group, was crucial in providing access to O-2-alkynylaryl N,N-diethyl carbamates by a direct alkynylation of the o-lithiated carbamate, with arylsulfonylalkynes as electrophilic reagents. Cyclization of the generated o-alkynylaryl carbamates was successfully accomplished through a strategy involving in situ carbamate alkaline hydrolysis under conventional heating or microwave irradiation, coupled with a subsequent heterocyclization step delivering the desired benzo[b]furans. A wide variety of new halobenzo[b]furans has been synthesized and their utility has been demonstrated by their further transformation.

Unlocking the 5-exo Pathway with the AuI -Catalyzed Alkoxycyclization of 1,3-Dien-5-ynes.

The first general regio- and stereoselective 5-exo gold(I)-catalyzed alkoxycyclization of a specific class of 1,5-enynes such as 1,3-dien-5-ynes has been described, despite 1,5-enynes being known to almost invariably proceed via endo cyclizations under gold-catalysis. The configuration of the terminal alkene in the starting 1,3-dien-5-yne plays a crucial role on the regiochemical outcome of the reaction. A wide variety of interesting alkoxy-functionalized alkylidenecyclopentenes have been synthesized from 1-monosubstituted (E)-1,3-dien-5-ynes. On the contrary, the corresponding Z isomers evolve affording formal 6-endo cyclization products. In addition, mechanistic exploration supports a highly stabilized carbocation as a key intermediate instead of a highly constrained cyclopropyl gold carbene from E isomers, and also accounts for the well differentiated reactivity observed between both E/Z geometrical isomers as well as for the stereochemical outcome of the reaction.

Gold(i)-catalyzed nucleophilic cyclization of ß-monosubstituted o-(alkynyl)styrenes: a combined experimental and computational study.

The stereospecific gold(i)-catalyzed nucleophilic cyclization of ß-monosubstituted o-(alkynyl)styrenes to produce C-1 functionalized 1H-indenes including challenging substrates and nucleophiles, such as ß-(cyclo)alkyl-substituted o-(alkynyl)styrenes and a variety of alcohols as well as selected electron-rich aromatics, is reported. DFT calculations support the stereochemical outcome of the process that involves the formation of a key cyclopropyl gold carbene intermediate through a regiospecific 5-endo cyclization.

Reductive Molybdenum-Catalyzed Direct Amination of Boronic Acids with Nitro Compounds.

The synthesis of aromatic amines is of utmost importance in a wide range of chemical contexts. We report a direct amination of boronic acids with nitro compounds to yield (hetero)aryl amines. The novel combination of a dioxomolybdenum(VI) catalyst and triphenylphosphine as inexpensive reductant has revealed to be decisive to achieve this new C-N coupling. Our methodology has proven to be scalable, air and moisture tolerant, highly chemoselective and engages both aliphatic and aromatic nitro compounds. Moreover, this general and step-economical synthesis of aromatic secondary amines showcases orthogonality to other aromatic amine syntheses as it tolerates aryl halides and carbonyl compounds.

General Synthesis of Alkenyl Sulfides by Palladium-Catalyzed Thioetherification of Alkenyl Halides and Tosylates.

The cross-coupling reaction of alkenyl bromides with thiols catalyzed by palladium complexes derived from inexpensive dppf ligand is reported. These reactions occur under low catalyst loading and in high yields and display wide scope, including the coupling of bulky thiols and trisubstituted bromoolefins, and functional group tolerance. In addition, the thioetherification of less reactive chloroalkenes and, for the first time, alkenyl tosylates was accomplished using a catalyst generated from CyPF tBu alkylbisphosphine ligand.

Gold(i)-catalyzed diastereoselective synthesis of 1-α-oxybenzyl-1H-indenes.

The gold(i)-catalyzed oxycyclization of ß-aryl monosubstituted o-(alkynyl)styrenes gives rise to 1-α-methoxy or 1-α-hydroxybenzyl-1H-indenes in a diastereospecific way. In contrast to ß,ß-disubstituted o-(alkynyl)styrenes, the stereochemical outcome of this process, diastereospecific reaction supports the higher contribution of a gold intermediate with a cyclopropylcarbene-like character.

Formal [4 + 1] Cycloadditions of ß,ß-Diaryl-Substituted ortho-(Alkynyl)styrenes through Gold(I)-Catalyzed Cycloisomerization Reactions.

Gold(I)-catalyzed cycloisomerization of ß,ß-diaryl-o-(alkynyl)styrenes at 80 °C selectively yields dihydroindeno[2,1-a]indenes in a transformation that encompasses a formal [4 + 1] cycloaddition and takes place through a cascade 5-endo-cyclization-diene activation-iso-Nazarov cyclization. In addition, by performing the reaction at 0 °C, the same substrates exclusively give rise to benzofulvene derivatives, which have also been shown to be intermediates in the formation of the tetracyclics.