Palladium(0)-Catalyzed Synthesis of Cross-Conjugated Polymers: Transformation into Linear-Conjugated Polymers through the Diels-Alder Reaction

A Pd-catalyzed highly selective three-component protocol for trisubstituted allenes

Herein we report the first example of a Pd-catalyzed highly selective three-component reaction of alkynyl-1,4-diol dicarbonates, organoboronic acids, and malonate anions for the efficient synthesis of trisubstituted 2,3-allenyl malonates not readily available by the known protocols. The reaction demonstrates an excellent regio- and chemo-selectivity for both the oxidative addition referring to the two C-O bonds and the subsequent coupling with the nucleophile with a remarkable functional group compatibility. A series of control experiments confirm a unique mechanism involving β-O elimination forming alka-1,2,3-triene and the subsequent insertion of its terminal C[double bond, length as m-dash]C bond into the Ar-Pd bond.

A General Stereoselective Synthesis of [4]Dendralenes

The first general synthesis of branched tetraenes ([4]dendralenes) involves two or three steps from inexpensive, commodity chemicals. It involves an unprecedented variation on Suzuki-Miyaura cross-coupling, generating two new C-C bonds in a one-flask operation with control of diastereoselectivity. The broad scope of the method is established through the synthesis of more than 60 diversely substituted [4]dendralene molecules, along with substituted buta-1,3-dienes and other [n]dendralenes. [4]Dendralenes are demonstrated to be significantly more kinetically stable than their well-known [3]dendralene counterparts. The first stereoselective synthesis of these compounds is also reported, through the catalyst-controlled generation of both E- and Z-diastereomeric products from the same precursor. Novel, through-conjugated/cross-conjugated hybrid molecules are introduced. The first selective dienophile cycloadditions to substituted [4]dendralenes are reported, thus paving the way for applications in target-oriented synthesis.

Palladium-Catalyzed Tail-to-Tail Reductive Dimerization of Terminal Alkynes to 2,3-Dibranched Butadienes

The palladium-catalyzed tail-to-tail reductive dimerization of terminal alkynes is described for the first time. Aromatic terminal alkynes bearing diverse and sensitive functional groups as well as aliphatic terminal alkynes are efficiently transformed to 2,3-dibranched butadienes. The key to achieve a selective tail-to-tail reductive dimerization reaction is to control appropriately the acidity of the reaction solution, which is accomplished by a combined use of pivalic acid and para-toluenesulfonic acid. The tail-to-tail reductive dimerization reaction is proposed to proceed via a cationic alkenyl palladium intermediate under acidic conditions.

Chain-end functionalization of living helical polyisocyanides through a Pd(ii)-mediated Sonogashira coupling reaction

Various functional helical polymers were constructed through chain-end functionalization of living helical polyisocyanides through a Pd(ii)-mediated Sonogashira coupling reaction.

Synthesis and Properties of 2,3-Diethynyl-1,3-Butadienes

The first general preparative access to compounds of the 2,3-diethynyl-1,3-butadiene (DEBD) class is reported. The synthesis involves a one-pot, twofold Sonogashira-type, Pd⁰ -catalyzed coupling of two terminal alkynes and a carbonate derivative of a 2-butyne-1,4-diol. The synthesis is broad in scope and members of this structural family are kinetically stable enough to be handled using standard laboratory techniques at ambient temperature. They decompose primarily through heat-promoted cyclodimerizations, which are impeded by alkyl substitution and accelerated by aryl or alkenyl substitution. An iterative sequence of these unprecedented Sonogashira-type couplings generates a new type of expanded dendralene. A suitably substituted DEBD carrying two terminal alkyne groups undergoes Glaser-Eglinton cyclo-oligomerization to produce a new class of expanded radialenes, which are chiral due to restricted rotation about their 1,3-butadiene units. The structural features giving rise to atropisomerism in these compounds are distinct from those reported previously.

Synthesis of π-conjugated network polymers based on triphenylamine (TPA) and tetraphenylethylene (TPE) as building blocks via direct Pd-catalyzed reactions and their application in CO2 capture and explosive detection

In this study, we report the synthesis of π-conjugated network polymers via palladium-catalyzed direct arylation polycondensation of triphenylamine (TPA) and tetraphenylethylene (TPE) with different active substrates. Moreover, six conjugated porous polymers were obtained (named as TPA-TPA-MA, TPA-PB-MA, TPA-TFB-MA, TPA-TPE-MA, TPE-PB-MA, and TPE-TFB-MA). Then, the fluorescence properties in the solid and dispersed states, the corresponding microporous structures, and the Brunauer–Emmett–Teller (BET) surface areas of all polymers were well studied. Among the obtained materials, TPA-PB-MA possessed not only largest BET surface area (686 m² g⁻¹) and largest pore volume (0.716 cm³ g⁻¹), but also the smallest pore size of 0.823 nm. These properties are very beneficial for the application of TPA-PB-MA in CO₂ storage and PA sensing. At 1 bar, TPA-PB-MA demonstrated the significant CO₂ uptake of 2.70 and 1.35 mmol g⁻¹ at 273 and 298 K, respectively. Furthermore, TPA-PB-MA was most sensitive and selective towards PA recognition. The K_SV constant was measured as 4.0 × 10⁴ M⁻¹.

In this study, we report the synthesis of π-conjugated network polymers via palladium-catalyzed direct arylation polycondensation of triphenylamine (TPA) and tetraphenylethylene (TPE) with different active substrates.

Synthesis of ene-yne-enes by nickel-catalyzed double SN2′ substitution of 1,6-dichlorohexa-2,4-diyne

1,6-Dichlorohexa-2,4-diyne undergoes nickel-catalyzed double substitution with aryl and alkenyl Grignard reagents to provide substituted ene-yne-enes.

Direct arylation of fluoroarenes toward linear, bent-shaped and branched π-conjugated polymers: polycondensation post-polymerization approaches

A direct arylation polycondensation of fluoroarenes with 2,7-dibromo-9,9-dioctylfluorene,F8, was achieved in a low polar solvent, toluene.