Cyclopropane Research Articles

Palladium-Catalyzed Living/Controlled Vinyl Addition Polymerization of Cyclopropenes.

Despite the various utilities of cyclopropenes (CPEs) in organic synthesis and ring-opening metathesis polymerization (ROMP), their vinyl addition polymerization has been sporadically explored, and the corresponding living/controlled polymerization remains a formidable challenge. The major obstacle is the intrinsic instability of the intermediate and the kinetic barrier for propagation. Herein a living/controlled vinyl addition polymerization of 3-methyl-3-carboxymethyl CPEs, catalyzed by [Pd(π-allyl)Cl]2 ligated by a sulfinamide bisphosphine ligand, is demonstrated. A plot of the number-average molecular weight (Mn) versus the conversion was found to be linear during the polymerization, with the molecular weight dispersity (Mw/Mn) remaining narrow. The Mn values increased linearly with the increase in the initial feed ratio of monomer to catalyst. Furthermore, controlled block copolymerization via sequential monomer addition was successful. All of these points corroborate the living nature of this polymerization. The synergistic coordination action of the catalyst ligand and the lateral carbonyl group in the cyclopropene moiety plays a key role in achieving the efficient polymerization in a living/controlled manner.

Cobalt-Catalyzed Enantioselective Hydroalkylation of Cyclopropenes with Cyclopropanols

Key words cobalt catalysis - cyclopropanes - cyclopropanols - hydroalkylation

Cobalt-Catalyzed Asymmetric Hydroalkylation of Cyclopropenes

Cobalt-Catalyzed Asymmetric Hydroalkylation of Cyclopropenes

Polymerization of Cyclopropenes: Taming the Strain for the Synthesis of Controlled and Sequence-Regulated Polymers.

Cyclopropenes (CPEs) are highly strained cyclic olefins, yet there are surprisingly limited examples leveraging their high strain energy for polymerization. In the past, attempts had been made to polymerize CPEs via cationic and insertion polymerization, but side reactions often gave uncontrolled polymers with mixed backbone structures. Ring-opening metathesis polymerization (ROMP) represents an ideal strategy for polymerizing CPEs to access new types of polymers. The proximity of substituents to the olefin in the small framework of CPEs offers a modular handle to tune the kinetic barrier to propagation by the modulation of the substituents. While the first few studies focused on the homopolymerization of simple alkyl or phenyl disubstituted CPEs, we recently explored the metathesis of a wide range of CPEs with different substituents using Grubbs catalysts and discovered surprising and diverse reactivities that are contingent on the positions, sterics, and electronics of substituents. The observed reactivities ranged from living homopolymerization to catalyst deactivation to single addition to the catalyst without homopropagation. In particular, the exclusively single addition reactivity found in two families of CPEs, with either bis(methanol ester) or phenyl and methanol ester substituents at the allylic position, is unusual for any monomer and perhaps counterintuitive for highly strained cycles. These single-addition CPEs could, however, be copolymerized with low-strain cyclic olefins to generate perfectly alternating copolymers with controlled molecular weights and low dispersity and to introduce degradable backbone linkages. A single equivalent (relative to the active chain end) of such CPEs could also be added to the active chain end of living ROMP polymers to install functional terminal groups or during living ROMP to place single units of functional moieties or side chains at any desired chain locations in narrow-disperse homopolymers and block copolymers. This account summarizes the polymerization of CPEs with a focus on our journey to uncover the rich and unique metathesis reactivities of CPEs and their utility in synthesizing well-controlled and sequence-regulated polymers. It provides the first collective structure-metathesis reactivity relationships for CPEs in the context of polymer chemistry and an understanding of the interactions between the catalyst and the substituents of appended ring-opened CPEs. It may become clear from this Account that the exploration of strained cycles in polymer chemistry can be quite fruitful in discovering new chemistry and accessing new types of polymer materials.

How Does the Guest—Host Hydrogen Bonding Affect the Thermal Properties of Clathrate Hydrates?

Herein, molecular dynamics simulations are performed to study the effect of the guest-host hydrogen bonding on the thermal properties, such as isothermal compressibility, isobaric thermal expansivity, and heat capacity, in the sI clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. The results of these simulations are compared with those of nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane (Et). Binary hydrates are constructed with the above guests in large 14-sided cages and methane placed in small 12-sided cages of the structure of sI clathrate hydrates. We present the temperature dependence of the lattice parameter and also the pressure dependence of the unit cell volume for variety guests with different sizes, polarity, and guest-host hydrogen bonding capability. The lattice parameters for some of the guest species obtained in this work are in good agreement with experimental values. The oxygen atom of the formaldehyde carbonyl group and the ether oxygen atoms of TMO and EO molecules can form hydrogen bonds with sI large cage water hydrogen atoms while CB, CP and Et molecules do not. The consequences of the guest-host hydrogen bonding on the isothermal compressibility, thermal expansivity, and heat capacity of the clathrate are discussed.

Hydroamination of Cyclobutenes and Cyclopropenes

Hydroamination of Cyclobutenes and Cyclopropenes

CYCLOPROPYLATION OF HETEROCYCLIC CORES USING CYCLOPROPYLBORONIC DERIVATIVES

Methods for cyclopropane ring incorporation into various heterocyclic cores using cyclopropylsubstituted organoboron compounds are surveyed. In particular, Suzuki–Miyaura and Chan–Lam reactions, recent coupling processes involving organotrifluoroborates, as well as C–H activation of heterocyclic substrates are discussed.

Preparation of Chiral Difluoromethyl Cyclopropenes

Preparation of Chiral Difluoromethyl Cyclopropenes

How does the guest—host hydrogen bonding affect the thermal properties of clathrate hydrates?

Herein, molecular dynamics simulations are performed to study the effect of the guest—host hydrogen bonding on the thermal properties, such as isothermal compressibility, isobaric thermal expansivity, and heat capacity, in the sI clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. The results of these simulations are compared with those of nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane (Et). Binary hydrates are constructed with the above guests in large 14-sided cages and methane placed in small 12-sided cages of the structure of sI clathrate hydrates. We present the temperature dependence of the lattice parameter and also the pressure dependence of the unit cell volume for variety guests with different sizes, polarity, and guest—host hydrogen bonding capability. The lattice parameters for some of the guest species obtained in this work are in good agreement with experimental values. The oxygen atom of the formaldehyde carbonyl group and the ether oxygen atoms of TMO and EO molecules can form hydrogen bonds with sI large cage water hydrogen atoms while CB, CP and Et molecules do not. The consequences of the guest—host hydrogen bonding on the isothermal compressibility, thermal expansivity, and heat capacity of the clathrate are discussed.

Palladium-Catalyzed[4+2] Annulation of Cyclopropenes with Benzosilacyclobutanes

Palladium-Catalyzed[4+2] Annulation of Cyclopropenes with Benzosilacyclobutanes

Tuning the Reactivity of Cyclopropenes from Living Ring‐Opening Metathesis Polymerization (ROMP) to Single‐Addition and Alternating ROMP

Ring-opening metathesis polymerization (ROMP) has become one of the most important living polymerizations. Cyclopropenes (CPEs) remain underexplored for ROMP. Described here is that the simple swap of 1-methyl to 1-phenyl on 1-(benzoyloxymethyl)CPEs elicited strikingly different modes of reactivity, switching from living polymerization to either selective single-addition or living alternating ROMP. The distinct reactivity stems from differences in steric repulsions at the Ru alkylidene after CPE ring opening. Possible olefin or oxygen chelation from ring-opened CPE substituents was also observed to significantly affect the rate of propagation. These results demonstrate the versatility of CPEs as a new class of monomers for ROMP, provide mechanistic insights for designing new monomers with rare single-addition reactivity, and generate a new functionalizable alternating copolymer scaffold with controlled molecular weight and low dispersity.

Tuning the Reactivity of Cyclopropenes from Living Ring‐Opening Metathesis Polymerization (ROMP) to Single‐Addition and Alternating ROMP

AbstractRing‐opening metathesis polymerization (ROMP) has become one of the most important living polymerizations. Cyclopropenes (CPEs) remain underexplored for ROMP. Described here is that the simple swap of 1‐methyl to 1‐phenyl on 1‐(benzoyloxymethyl)CPEs elicited strikingly different modes of reactivity, switching from living polymerization to either selective single‐addition or living alternating ROMP. The distinct reactivity stems from differences in steric repulsions at the Ru alkylidene after CPE ring opening. Possible olefin or oxygen chelation from ring‐opened CPE substituents was also observed to significantly affect the rate of propagation. These results demonstrate the versatility of CPEs as a new class of monomers for ROMP, provide mechanistic insights for designing new monomers with rare single‐addition reactivity, and generate a new functionalizable alternating copolymer scaffold with controlled molecular weight and low dispersity.

Characterization of products from sawdust biodegradation using selected microbial culture isolated from it

Characterization of products from sawdust degradation using selected microbial culture isolated from it was carried out. A composite sawdust waste sample was collected from MCC timber market in Calabar. The sample was diluted using serial dilution method and inoculated on Nutrient agar and Sabauraud dextrose agar using pour plate technique and incubated at 370C and 270C respectively. Five bacteria species and 3 species of fungi were identified which included Bacillus sp, Serracia mercescens, Micrococcus sp, Pseudomonas aeruginosa, Streptococcus sp, Aspergillus niger, Rhizopus sp and Penicillumsp. The bacteria and fungi species were individually and in combination inoculated into sterile sawdust containing sterile water. These were kept at 270C for 21 days. Protein, glucose contents and chemical components in the degraded sawdust samples were determined using GC-MS chromatography. It was observed that Aspergillus niger degradation had protein content 7.87g/l, Serracia mercescens and Aspergillus niger 6.56g/l, and Serracia mercescens 5.75g/l. These organisms used lignocellulolytic enzymes and similar enzymes in the degradation process. In the case of glucose, the combined degradation produced 2.24g/l, Aspergillus niger 2.05g/l and Serracia mercescens 1.94g/l. It was also observed that sawdust inoculated with Serratia marcescens produced 14 compounds while the combined species of Aspergillus niger and Serratia marcescens produced only 12 compounds. The following compounds Methylene cyclo propane carboxylic acid, Glycine N-Cyclopropylcarbonyl-methyl ester, acetic acid, propanoic acid, benzaldehyde, thiophene, tetrahydro, furfural and propanoic acid 2,2-Dimethyl-2-ethylhexyl ester were detected from the combination of Serratia marcescens and Aspergillus niger though in different concentrations. The percent concentrations of the compounds from Serratia marcescens range from n-Hexadecanoic acid 3.59 to Methylene cyclo propane carboxylic acid with 11.56 while Serratia marcescens and Aspergillus niger range from Butanoic acid, 4-chloro 3.59 to Benzaldehyde with 11.56. Microbial degradation of sawdust produced economically important products and therefore can contribute to the economy of this country at the same time reduce pollution caused by it which is a novel. Key words: Sawdust, biodegradation, bioactive, extracts, microbial culture, lignocellulosic.

N-Acetyl-Directed Cyclopropanation of Indoles

N-Acetyl-Directed Cyclopropanation of Indoles

Precise Placement of Single Monomer Units in Living Ring-Opening Metathesis Polymerization

Summary Precise control of the location and sequence of monomers in a narrow-disperse polymer chain remains a significant challenge. Our strategy uses selective and quantitative single additions of cyclopropene (CPE) derivatives to precisely place functional moieties at desired locations along a polymer chain during the living ring-opening metathesis polymerization (ROMP) of norbornenes (NBEs). In order to completely reinitiate the chain end after single addition of a CPE, we lowered the reaction temperature and added a labile ligand. Under our optimized conditions, we demonstrated the exclusive placement of single moieties at pre-determined locations along a polynorbornene (PNBE) homo or block co-polymer while maintaining narrow MW distributions and controlled MWs. Some polymers were used to synthesize precisely controlled branched architectures. The ability to control the location and number of individual functional groups in a polymer chain opens exciting opportunities for the precise synthesis and manipulation of polymer structures, architectures, assemblies, and properties.

Iridium-Catalyzed Enantioselective C(sp3)–H Borylation of Cyclopropanes

Iridium-Catalyzed Enantioselective C(sp3)–H Borylation of Cyclopropanes

RECENT ADVANCES IN (HETERO)CYCLIZATIONS OF N -VINYLAZOLES

Recent advances in chemistry of N -vinylazoles are surveyed in this microreview, including results published in the last decade. In particular, reactions involving double bond of N -vinylazoles and formation of new cycles are discussed. These transformations include cycloadditions, cyclopropane syntheses, and heterocyclizations based on the CH activation.

Visible-Light-Mediated Cyclopropane Construction

Visible-Light-Mediated Cyclopropane Construction

The thermal properties of binary structure sI clathrate hydrate from molecular dynamics simulation

ABSTRACTIn this work, we present temperature dependence of lattice parameter and normalised lattice parameter in the atmospheric pressure and 120 bar and also pressure dependence of unit cell volume and normalised unit cell volume at 150 and 250 K for variety guests with different size, polarity and guest–host hydrogen bonding capability such as trimethylene oxide (TMO), ethylene oxide (EO), formaldehyde (FA), cyclobutane (CB), cyclopropane (CP) and ethane (Et) in the large cages with CH4 in small cages of sI clathrate hydrates by molecular dynamics simulations. The obtained values of lattice parameters for the guest species are compatible with the experimental values. These clathrate hydrates are simulated with TIP4P/ice four-site water potential. Herein, isobaric thermal expansivity and isothermal compressibility are calculated at a temperature range of 50–250 K and a wide pressure range. These structural properties have been compared for guests which they are isoelectronic and have similar masses but with different size and polarity. We use molecular dynamics simulations to relate microscopic guest properties, like guest–host hydrogen bonding to macroscopic sI clathrate hydrate properties. The temperature dependence of thermodynamic properties such as constant-volume and constant-pressure heat capacity is presented in the atmospheric pressure for these guest species.

The distinctly Canadian origins of cyclopropane.

The distinctly Canadian origins of cyclopropane.