Polymeric Blatter's Radical via CuAAC and ROMP Saal, Adrian; Friebe, Christian; Schubert, Ulrich S.
Macromolecular chemistry and physics,
October 2021, 2021-10-00, 20211001, Letnik:
222, Številka:
19
Journal Article
Recenzirano
Odprti dostop
A Blatter radical‐containing polymer backbone is synthesized via copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) and consecutive ring‐opening metathesis polymerization. For this, an ...alkyne‐functionalized Blatter radical is synthesized and used for the described CuAAC, yielding a polymerizable derivative of the radical. The resulting polymer is electrochemically investigated in cyclic voltammetry experiments, paving the way for the possible utilization of triazinyl radicals in all‐organic polymer batteries. Furthermore, the simple modification of the alkyne bond makes further derivatization easily accessible.
A Blatter radical‐containing polymer is designed and synthesized via ring‐opening metathesis polymerization and further characterized electrochemically. The monomeric structure is prepared by coupling an alkyne‐functionalized Blatter radical with a norbornene structure in a copper‐catalyzed alkyne‐azide cycloaddition (CuAAC). This type of reaction is especially promising for an easy modification of the radicals under mild conditions.
We report an efficient semihydrogenation of terminal alkynes with H2, catalyzed by a modified, tetramethylated PNP pincer Fe hydride complex. The reactivity contrasts with an analogous classical PNP ...Fe hydride complex containing CH2 arms, which catalyzes predominantly terminal alkyne dimerization even in the presence of H2, and with an N-Me arm PNP Fe complex, which is known to cause overreduction to alkanes and requires the presence of a trimethylsilyl protective group. Such straightforward PNP ligand modification is a convenient tool that switches reactivity and leads to selective alkene formation, with no dimerization side products observed and only a minor contribution from overreduction.
containing heterocyclic scaffolds by virtue of their interesting reactivities and a broad range of applications in the medicinal and materials chemistry. This review involves the ...electrophilic/radical cyclization of alkynes containing heteroatoms which resulted into the novel Se‐heterocycles. The synthesis of seleno‐heterocycles via different nucleophiles including O, N, S, Se, Te, and C‐nucleophiles is exhaustively discussed. Also, one‐pot electrophilic cyclization of 1,3‐diynes and 1,3,5‐triynes was described in details. Furthermore, the various mechanisms underlying the synthesis of selenium‐β‐lactam, carbapenem heterocycle, bis‐ and tris‐selenide alkene, β‐selenosulfonation and selenated alkynes were discussed. The Se‐heterocycles reported in this review allow preparing these selenated compounds bearing the selenium moiety both on the rings (outside) and inside the ring (e. g. selenophenes). The review demonstrates the growing opportunities to construct selenium containing heterocycles from alkynes containing heteroatoms.
Homogeneous Catalysis The palladium‐catalyzed tail‐to‐tail reductive dimerization of terminal alkynes to 2,3‐dibranched butadienes is reported by Yang Li, Ming Bao et al. in their Communication ...(e202116870).
Cyclopentenes and indenes are important structural scaffolds in synthetic, medical, and material chemistry. Cyclization of alkynes via remote C−H functionalization is an appealing approach to ...construct these motifs due to its high efficiency and step‐economy. Herein, a traceless directing group strategy was designed to reverse the regioselectivity of radical addition which enabled an unprecedented photocatalytic sulfonylcarbocyclization of terminal alkynes by forming C−C bond on inert C(sp3)−H bond. It offers a facile access to decorated cyclopentenes and indenes under mild conditions. The resultant products could be converted into a set of valuable molecular scaffolds, including a key intermediate of AM‐6226. Mechanistic experiments suggest a radical cascade pathway comprising a Markovnikov‐type sulfonylation, 1,5‐hydrogen atom transfer, 5‐endo‐trig cyclization, and β‐elimination. This study lays further groundwork for the use of anti‐Baldwin 5‐endo‐trig radical cyclization in rapidly assembling five‐membered carbocycles.
A photocatalytic sulfonylcarbocyclization of terminal alkynes using SEt as a traceless directing group is developed, providing a facile access to highly substituted cyclopentenes and indenes from readily available starting materials. It represents a new advance on anti‐Baldwin 5‐endo‐trig radical cyclization of all‐carbon systems, which may be valuable for the fast construction of five‐membered carbocycles.
8-Quinolinolate is a monoanionic, hard, strongly σ-donating ligand that can form strong chelates with various metals. However, studies of the catalytic activities of soft transition metal complexes ...such as greater than second row, low-valent, late-transition metals having 8-quinolinolate ligands had not been well explored until recently. In recent years, several research groups including our own have studied and developed various reactions of terminal alkynes using rhodium(I) catalysts containing an 8-quinolinolate ligand. In this Perspective, we surveyed the transformations of terminal alkynes using 8-quinolinolato rhodium(I) catalyst such as additions of alcohols, amines, and thiols as well as polymerization, trimerization, dimerization, and alkyne/alkene 2 + 2 cycloaddition. Mechanistic studies based on theoretical calculations of hydroalkoxylation of alkynes and alkyne/alkene 2 + 2 cycloaddition reactions have also been described.
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.
The use of a combination of pivalic acid and para‐toluenesulfonic acid proved successful in favoring the selective highly chemo‐ and regioselective tail‐to‐tail reductive dimerization of terminal alkynes over the competitive head‐to‐tail dimerization pathway. The target reaction, proposed to proceed via a cationic alkenyl palladium intermediate, presents a facile and straightforward approach for accessing 2,3‐dibranched butadienes.
The first total synthesis of a tetracyclic marine pyridinium alkaloid hinged on recent advances in chemoselectivity management: While many classical methods failed to afford the perceptively simple ...pyridine‐containing core of the target, nickel/iridium photoredox dual catalysis allowed the critical C−C bond to be formed in good yield. Likewise, ring closing alkyne metathesis (RCAM) worked well in the presence of the unhindered pyridine despite the innately Lewis acidic Mo(+6) center of the alkylidyne catalyst. Finally, an iridium catalyzed hydrosilylation was uniquely effective in reducing a tertiary amide without compromising an adjacent pyridine and the lateral double bonds; this transformation is largely without precedent. The second strained macrocycle enveloping the core was closed by intramolecular N‐alkylation with formation of the pyridinium unit; the reaction proceeded site‐ and chemoselectively in the presence of an a priori more basic tertiary amine.
The conquest of a polycyclic marine pyridinium alkaloid was only made possible by the remarkable chemoselectivity profile of contemporary transition metal catalysts that operate in the presence of basic sites. Ni/Ir photoredox catalysis, Mo‐alkylidynes for alkyne metathesis, and an Ir‐catalyzed lactam‐selective hydrosilylation stand out in this regard.
Abstract
A new route to the macrolactone antibiotic berkeleylactone A was developed. As a key step, a ring‐closing alkyne metathesis (RCAM) of an ester substrate featuring 1‐propynyl termini was ...used. The carboxylic part of the substrate was easily assembled using alkyne chemistry, like carboxylation of a diyne followed by isomerization of the ynoate section to a dienoate and dihydroxylation of the 4,5‐double bond. The synthesis of the alcohol part of the ester started with opening of (
R
)‐propylene oxide with an acetylide and was followed by two triple bond migrations. After successful RCAM which formed the C8−C9 bond, the triple bond was selectively hydrogenated to the corresponding alkene before the 4,5‐diol was oxidized to the 5‐hydroxy‐4‐oxo derivative. At this stage, the thioether was formed and the 8,9‐double bond reduced. We also prepared the 8,9‐didehydro analog of berkeleylactone A. However, it turned out that its antimicrobial activity was slightly reduced.
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