Propargylic Carbonates Research Articles

Construction of Vicinal All-Carbon Stereogenic Centers via Copper-Catalyzed Asymmetric Decarboxylative Propargylation: Enantio- and Diastereoselective Synthesis of Substituted Spirolactones

The formation of vicinal all-carbon quaternary stereocenters remains a formidable challenge. We report herein the synthesis of such highly congested structural dyads by copper-catalyzed decarboxylative propargylation between propargyl carbonates and indanone-based nucleophiles. The implementation of diphenylethylenediamine (DPEN)-based ligands is the key to success. A wide range of functional groups was tolerated, delivering the indanone-based spirolactones in good yields with high diastereo- and enantioselectivity. The mechanistic observations suggest the capability of the new copper complex to enable stereocontrolled addition to copper-allenylidene species.

Copper-Catalyzed C(3+1) copolymerization of propargyl carbonates and aryldiazomethanes

Controlling the composition and sequence during diazo copolymerization with vinyl or acetylenic monomers is highly desired yet challenging. Here we report a new base-metal-catalysis strategy to address this problem via tandem coupling/polymerization. A selective Cu-catalyzed C(3+1) copolymerization reaction was developed using propargyl carbonates and aryldiazomethanes derived from N-tosylhydrazones as the C3 and C1 building blocks, respectively. This reaction rapidly produces alternating-like poly(1,4-diaryl-2-butyne-1,4-diyl)s (Mn up to 31.0 kg/mol) in a modular fashion, without detectable homopolymer segments. This work provides a new avenue for the synthesis of hydrocarbon polymers through diazo copolymerization.

Glucose‐derived superabsorbent hydrogel materials based on mechanically‐interlocked slide‐ring and triblock copolymer topologies

AbstractA series of glucose‐based degradable superabsorbent hydrogels with potential to tackle issues associated with sustainability, flooding, and drought has been designed and fabricated. These hydrophilic networks were constructed through integrating glucose as a primary building block –into cyclic oligomers and block polymers, which were combined into mechanically‐interlocked slide‐ring crosslinked materials. Crosslinking of slide ring α‐cyclodextrin/poly(ethylene glycol)‐type polyrotaxanes with acid‐functionalized ABA triblock copolymers comprised of mercaptopropionic acid‐functionalized poly(glucose carbonate (ethyl propargyl carbonate))‐b‐poly(ethylene glycol)‐b‐mercaptopropionic acid‐functionalized poly(glucose carbonate (ethyl propargyl carbonate)), afforded degradable superabsorbent hydrogels through establishment of chemically‐labile ester linkages, in addition to glycosidic and carbonate groups of the polymer precursors. With an emphasis on development of fundamental synthetic design strategies to achieve high‐performance superabsorbent hydrogels that could behave as robust materials, which are derived from natural components and exhibit hydrolytic degradability, effort went into optimization of the composition, structure, and topology leading to water uptake capacities >30× by mass. Investigations of composition‐structure‐topology‐morphology effects on properties as a function of variations of PEG main chain length, degree of α‐cyclodextrin coverage, and concentration of pre‐gel solution, indicated that the slide‐ring polymer and triblock copolymer networks feature high water uptake, tunable mechanical properties, and sustainability with construction from renewable natural products and in‐built degradability.

Palladium-catalyzed regioselective synthesis of mono and bis(arylthiol) alkenes from propargyl carbonate and thiophenol.

A palladium catalyzed regioselective reaction of propargylic carbonate with thiophenols and benzene selenol is described. Atom-economic addition of thiols to propargylic carbonates provides an excellent opportunity for effective processes. The reaction proceeds via hydrothiolation to produce mono(arylthiol) alkenes and hydrothiolation followed by Tsuji-Trost type substitution to form bis(arylthiol) alkenes through single and double sequential attack by soft thio nucleophiles by control of the equivalence of thiophenols. This coupling reaction with good tolerance towards functional groups in both propargylic carbonates and thiols furnished a variety of highly functionalized alkenylation products in moderate to excellent yields via the formation of new C-S and C-Se bonds.

Palladium-catalyzed allylic allenylation of homoallyl alcohols with propargylic carbonates

A palladium-catalyzed reaction of homoallyl alcohols with propargylic carbonates was realized via oxidative addition/decarboxylation/retro-allylation.

Organocatalytic allylic alkylation of alkyne-substituted MBH carbonates: access to quaternary carbon-containing 1,4-enynes.

A DABCO-catalyzed allylic alkylation of tertiary propargylic alcohol-derived MBH carbonates with nitromethane was developed. A series of substituted 1,4-enynes with an all-carbon quaternary stereocenter were efficiently obtained in moderate to high yields. The synthetic utility of the product was demonstrated by facile synthesis of 1,4-enyne-embedded 2-pyrrolidinones.

Copper-catalyzed silylation of propargyl carbonates: a general entry to allenylsilanes

A copper-catalyzed silylation of propargyl carbonates with silylboranes affords structurally diverse allenylsilanes including tri- or tetra-substituted and 1,1- or 1,3-disubstituted allenylsilanes.

Nickel-Catalyzed Asymmetric Propargylation for the Synthesis of Axially Chiral 1,3-Disubstituted Allenes.

The general enantioselective catalytic synthesis of axially chiral 1,3-disubstituted allenes from readily available racemic propargylic alcohol derivatives remains a long-standing challenge in organic synthesis. Here we report an efficient nickel-catalyzed asymmetric propargylic substitution reaction/Myers rearrangement of racemic propargylic carbonates that furnishes a series of enantioenriched 1,3-disubstituted allenes using newly designed N-sulfonylhydrazone reagents as efficient diazo surrogates. This reaction proved to be remarkably general with regard to substrate scope, affording a diverse range of 1,3-disubstituted allenic compounds in good yields with excellent enantioselectivities. Additionally, applications of this powerful strategy for the enantioselective synthesis of methyl (S)-8-hydroxyocta-5,6-dienoate, (S)-laballenic acid, (S)-phlomic acid, and (S)-Δ9,10-pentacosadiene are described, further highlighting the broad potential of these new reagents for the discovery of novel reactions.

Enantioselective Construction of Vicinal Quaternary-Tetrasubstituted Carbon Stereocenters by Copper-Catalyzed Decarboxylative Propargylic Substitution.

Enantioselective construction of vicinal tetrasubstituted carbon stereocenters is a formidable challenge in organic synthesis. A copper-catalyzed asymmetric decarboxylative propargylic substitution with 3-amino oxindoles as trisubstituted carbon nucleophiles and propargylic cyclic carbonates as tertiary carbon electrophiles was developed. A range of 3-amino-3,3'-disubstituted oxindoles bearing vicinal quaternary-tetrasubstituted carbon stereocenters were obtained in high yields and good to excellent stereoselectivities (up to 98% yield, >20:1 dr, and 98.5:1.5 er).

Silver-anchored porous aromatic framework for efficient conversion of propargylic alcohols with CO2 at ambient pressure

The conversion of propargylic alcohols and carbon dioxide (CO2) into fine chemicals suffers from issues of harsh reaction conditions and difficult catalyst recovery. To achieve efficient CO2 activation at low energy consumption, a silver-anchored porous aromatic framework catalyst Ag@PAF-DAB with high active phase density and CO2 adsorption capacity was proposed. Since Ag@PAF-DAB has the dual functions of CO2 capture and conversion, propargylic alcohols were completely converted into α-alkylidene cyclic carbonate or α‑hydroxy ketone as high value-added product under atmospheric pressure (CO2, 0.1 MPa) and low silver equivalent (0.5 mol%). Notably, Ag@PAF-DAB exhibited broad substrate diversity, high stability, and excellent reusability. By applying FTIR and GC, the key to green synthetic route of α‑hydroxy ketone was confirmed to lie in the further hydration of α-alkylidene cyclic carbonate.

Iridium(III)-Catalyzed Regioselective B(4)–H Allenylation of o-Carboranes by Ball Milling

We disclose an iridium(III)-catalyzed regioselective B(4)-H allenylation of o-carboranes from o-carborane acids and propargyl carbonates under ball-milling conditions. This study sheds light on a novel method to accomplish regioselective B(4)-allenylation of o-carborane that cannot be realized through conventional solution-based reactions. Control experiments, including solution, neat, microwave, and high-temperature reactions, reveal that the B(4)-H allenylation of o-carborane is unique for ball-milling conditions.

Synthesis of conjugated bisallenes by cooperative Cu/Pd-catalysed borylallenylation of 2-trifluoromethyl-1,3-enynes.

A cooperative Cu/Pd-catalysed borylallenylation of 2-trifluoromethyl-1,3-enynes with propargylic carbonates under mild reaction conditions was developed. This method provides facile and efficient access to conjugated bisallenes with a broad range of functional groups. Both aromatic and aliphatic 1,3-enynes can be utilized in this transformation to give the corresponding multi-substituted conjugated bisallenes.

Cp*Rh(iii)-catalyzed and solvent-controlled tunable [4 + 1]/[4 + 3] annulation for the divergent assembly of dihydrobenzo[cd]indoles and dihydronaphtho[1,8-bc]azepines

A Cp*Rh-catalyzed solvent-switched tunable [4 + 1]/[4 + 3] cyclization of free 1-naphthylamines with propargyl carbonates is developed, providing dihydrobenzo[cd]indoles and dihydronaphtho[1,8-bc]azepines in moderate to good yields and broad range of functional groups.

Quantum chemistry study on the promoted reactivity of substituted cyclooctynes in bioorthogonal cycloaddition reactions

AbstractIn the present research, we focus on the energetics and electronic aspects of enhanced reactivity in the regioselective bioorthogonal 1,3-dipolar cycloaddition reaction of various substituted cyclooctynes with methyl azide, applying quantum chemistry approaches. In this respect, we assessed the structural and energetic properties of regioisomeric products and their corresponded transition states and calculated the reaction electronic energy changes and energy barriers through the cycloaddition pathways. The obtained results revealed that the trifluoromethyl substitution and fluorination of cyclooctynes lead to improved reactivity, in conjunction with increased exothermicity and decreased activation energy values. On the other hand, quantum theory of atoms in molecules computations were performed on some key bond and ring critical points that demonstrated the stabilizing topological properties of electron density and its derivatives upon trifluoromethyl substitution and fluorination of propargylic carbon of cyclooctynes which can be regarded as the essential origin of enhanced reactivity.

Non-Noble-Metal Metal–Organic-Framework-Catalyzed Carboxylative Cyclization of Propargylic Amines with Atmospheric Carbon Dioxide under Ambient Conditions

The coupling reaction of propargylic amines and carbon dioxide (CO2) to synthesize 2-oxazolidinones is an important reaction in industrial production, and yet harsh reaction conditions and noble-metal catalysts are often required to achieve high product yields. Herein, one novel noble-metal-free three-dimensional framework, [Mg3Cu2I2(IN)4(HCOO)2(DEF)4]n (1), assembled by magnesium and copper clusters was synthesized and applied to this reaction. Compound 1 displays excellent solvent stability. Importantly, 1, acting as heterogeneous catalyst, can highly catalyze the cyclization of propargylic amines with CO2 under atmospheric pressure at room temperature, which can be recycled at least five times without an obvious decrease of the catalytic activity. NMR spectroscopy, coupled with 13C-isotope- and deuterium-labeling experiments, clearly clarifies the mechanism of this catalytic system: CO2 was successfully captured and converted to the product of 2-oxazolidinones, the C≡C bond of propargylic amines can be effectively activated by 1, and proton transfer was involved in the reaction process. Density functional theory calculations are further conducted to uncover the reaction path and the crucial role of compound 1 during the reaction.

Enantioselective synthesis of indenopyrazolopyrazolones enabled by dual directing groups-assisted and rhodium(III)-catalyzed tandem C-H alkenylation/[3 + 2] stepwise cycloaddition

The CpXRh(III)-catalyzed asymmetric cascade C-H coupling/intramolecular cyclization of azomethine imines with propargyl carbonates has been developed, affording a variety of chiral tetracyclic indenopyrazolopyrazolone frameworks with good substrate/functional group tolerance and enantioselectivity (up to 97:3 er). Combined experimental studies and DFT calculations revealed the Rh(III)-catalyzed stepwise annulation process and clarified the synergy coordination mode of dual directing groups in tuning the selectivity.

Propargylic Amination Enabled the Access to Enantioenriched Acyclic α-Quaternary α-Amino Ketones.

A propargylic amination approach toward chiral acyclic α-quaternary α-amino ketones is described. This Cu-catalyzed procedure could be performed open to air using commercially available amines as nucleophiles. The key to success is the use of rationally designed propargylic cyclic carbonates as substrates, which can generate a Cu-bonded enolate zwitterionic intermediate upon decarboxylation. This protocol features wide functional group tolerance and high asymmetric induction, with typical ee value higher than 93%, and thus advances a great step forward in the challenging synthesis of acyclic chiral α-quaternary α-amino ketones.

Nickel-catalyzed Asymmetric Propargylic Amination of Propargylic Carbonates with Aniline Derivatives

A study for the development of the nickel-catalyzed highly enantioselective propargylic amination of propargylic carbonates with aniline derivatives is described. The reaction of internal alkyne-substituted propargylic carbonates with a series of aniline derivatives smoothly proceeded in DMSO using a combination of Ni(cod)2 and (R)-SEGPHOS as the catalyst to give the corresponding chiral propargylic amines in 61–93% yields with 91–97% ee (24 examples).

Poly(sulfone-carbonate-carborane) copolymers for rapid revelation of thermal neutron induced alpha tracks

The paper describes the preliminary studies regarding development of a new polymeric track detector known as poly (SDAC-co-ADC-co-APCC) for rapid detection of thermal neutrons induced alpha tracks. The polymeric detector with different percentages of natural boron (1–5%) content is prepared by cast copolymerization of Allyl Diglycol Carbonate (ADC) with Allyl Propargyl Carbonate Carborane (APCC) and 2,2′-Sulfonyl Diethanol bis (Allyl Carbonate) [SDAC]. APCC contains boron which increased thermal neutron sensitivity as boron has high cross-section for thermal neutrons. The etching conditions are optimized for this new polymeric detector and are 1 N NaOH at 60 °C for 30 minuets. It is noted that 3% boron containing poly (SDAC-co-ADC-co-APCC) detector is more sensitive than imported commercial (PADC)th and poly (APCC-co-ADC) detectors. It is observed that, in terms of number of net tracks developed, 3% boron containing poly (SDAC-co-ADC-co-APCC) detector is two and half times more efficient than (PADC)th and its signal to noise (S/N) ratio is almost two fold higher than that of (PADC)th ana poly (APCC-co-ADC). The optimized time for revelation of the tracks is 30 min [1 N NaOH at 60 °C] which is found to be one-fourth than that for (PADC)th and poly (APCC-co-ADC) [120 min in 6 N KOH at 70 °C].

Synthesis of Spirooxindoles Bearing 1,3‐Oxathiolane‐2‐thione Moiety From Isatin‐Derived Propargylic Alcohols

Spirooxindoles bearing 1,3‐oxathiolane‐2‐thione moiety were synthesized from isatin‐derived propargylic alcohols and carbon disulfide in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU). The spirooxindoles were formed stereoselectively via attack of the alkoxide of propargylic alcohol to carbon disulfide to form xanthate anion and a following 5‐exo‐dig cyclization process.