Addition of Imidazolium-Based Ionic Liquid to Improve Methanol Production in Polyamine-Assisted CO2 Capture and Conversion Systems Using Pincer Catalysts.

Ionic liquids have been studied as CO2 capture agents. However, they are rarely used in combined CO2 capture and conversion processes. Utilizing imidazolium-based ionic liquids, the conversion of CO2 to methanol was greatly improved in polyamine assisted systems catalyzed by homogeneous pincer catalysts with Ru and Mn metal centers. Among the ionic liquids tested, [BMIM]OAc was found to perform the best under the given reaction conditions. Among the polyamine tested, pentaethylenehexamine (PEHA) led to the highest conversion rates. Ru-Macho and Ru-Macho-BH were the most active catalysts. Direct air capture utilizing PEHA as the capture material was also demonstrated and produced an 86 % conversion of the captured CO2 to methanol in the presence of [BMIM]OAc.

Recent Advances in Visible Light-Mediated Radical Fluoro-alkylation, -alkoxylation, -alkylthiolation, -alkylselenolation, and -alkylamination.

In the last few years, many reagents and protocols have been developed to allow for the efficient fluorofunctionalization of a diverse set of scaffolds ranging from alkanes, alkenes, alkynes, and (hetero)arenes. The concomitant rise of organofluorine chemistry and visible light-mediated synthesis have synergistically expanded the fields and have mutually benefitted from developments in both fields. In this context, visible light driven formations of radicals containing fluorine have been a major focus for the discovery of new bioactive compounds. This review details the recent advances and progress made in visible light-mediated fluoroalkylation and heteroatom centered radical generation.

Photoredox Catalysis for the Synthesis of N-CF2 H Compounds Using 1-((N-(difluoromethyl)-4-methylphenyl)-sulfonamido)pyridin-1-ium Trifluoromethanesulfonate.

N-(difluoromethyl)amino (-NCF2 H) compounds are of great interest given their unique and underexplored physiochemical properties. The lack of structural diversity in NCF2 H compounds is likely due in part to the shortage of protocols for efficient installation. Presented herein is a new shelf-stable pyridinium reagent that enables the direct installation of the N-(difluoromethyl)sulfonamide moiety [N(Ts)CF2 H)] onto (hetero)arenes and alkenes for the diversification of aryl and alkyl NCF2 H compounds. The described protocol utilizes blue light photoredox catalysis and displays broad functional group tolerance with excellent chemoselectivity. Additional transformations and applicability towards a photoredox continuous flow protocol are also demonstrated.

Homogeneous Hydrogenation of CO2 and CO to Methanol: The Renaissance of Low-Temperature Catalysis in the Context of the Methanol Economy.

The traditional economy based on carbon-intensive fuels and materials has led to an exponential rise in anthropogenic CO2 emissions. Outpacing the natural carbon cycle, atmospheric CO2 levels increased by 50 % since the pre-industrial age and can be directly linked to global warming. Being at the core of the proposed methanol economy pioneered by the late George A. Olah, the chemical recycling of CO2 to produce methanol, a green fuel and feedstock, is a prime channel to achieve carbon neutrality. In this direction, homogeneous catalytic systems have lately been a major focus for methanol synthesis from CO2 , CO and their derivatives as potential low-temperature alternatives to the commercial processes. This Review provides an account of this rapidly growing field over the past decade, since its resurgence in 2011. Based on the critical assessment of the progress thus far, the present key challenges in this field have been highlighted and potential directions have been suggested for practically viable applications.

gem-Halofluorocyclopropanes via [2 + 1] Cycloadditions of In Situ Generated CFX Carbene with Alkenes.

An efficient and operationally simple synthesis of gem-bromofluorocyclopropanes under mild conditions has been developed. The method employs ethyl dibromofluoroacetate (EDBFA) as an accessible and inexpensive source of the bromofluorocarbene (:CFBr) intermediate. The protocol provides the bromofluorocyclopropane products in excellent yields, including examples synthesized in multigram scales. The chlorinated ester, ethyl dichlorofluoroacetate (EDCFA), is also utilized to make the analogous gem-chlorofluorocyclopropanes.

Nickel and Copper Catalyzed ipso-Phosphonodifluoromethylation of Arylboronic Acids with BrCF2 P(O)(OEt)2 for the Synthesis of Phosphonodifluoromethylarenes.

A convenient method for the direct ipso-phosphonodifluoromethylation of arylboronic acids via nickel-copper co-catalysis is disclosed. This work, which utilizes inexpensive first row transition metals, represents a facile alternative to the traditional palladium catalyzed approach. The method utilizes inexpensive commodity chemicals and substrates while tolerating a variety of biologically relevant functional groups. Structurally diverse phosphonodifluoromethylarenes are furnished in good yields under short reaction times. Control experiments to probe possible reaction pathways are also included.

C(sp2)-H Trifluoromethylation of enamides using TMSCF3: access to trifluoromethylated isoindolinones, isoquinolinones, 2-pyridinones and other heterocycles.

A method for the direct C(sp2)-H trifluoromethylation of enamides, including biologically relevant isoindolinones, isoquinolinones and 2-pyridinones using TMSCF3 under oxidative conditions is presented. The protocol is convenient, operationally simple and exhibits high tolerance across a multitude of relevant handles and functional groups.

Benzodiazines: recent synthetic advances.

Benzodiazines (diazonaphthalenes with both nitrogens in the same ring) - cinnolines (1,2-benzodiazine), quinazolines (1,3-benzodiazine), phthalazines (2,3-benzodiazine) and quinoxalines (1,4-benzodiazine) - are important class of compounds with broad biological properties and wide application in pharmaceutical as well as agrochemical arenas. These diazaheterocycles are present in a wide variety of bioactive natural products as well as synthetic molecules that are good drug candidates constituting key structural units responsible for their pronounced therapeutic activities. Their rapidly growing uses and applications in medicinal and agrochemical arenas prompt the researchers for further studies on this important group of compounds. In this review, we hope to provide a brief overview of the important general methodologies and recent developments towards their synthesis and open the door for further progress in this area.

Recycling of carbon dioxide to methanol and derived products - closing the loop.

Starting with coal, followed by petroleum oil and natural gas, the utilization of fossil fuels has allowed the fast and unprecedented development of human society. However, the burning of these resources in ever increasing pace is accompanied by large amounts of anthropogenic CO2 emissions, which are outpacing the natural carbon cycle, causing adverse global environmental changes, the full extent of which is still unclear. Even through fossil fuels are still abundant, they are nevertheless limited and will, in time, be depleted. Chemical recycling of CO2 to renewable fuels and materials, primarily methanol, offers a powerful alternative to tackle both issues, that is, global climate change and fossil fuel depletion. The energy needed for the reduction of CO2 can come from any renewable energy source such as solar and wind. Methanol, the simplest C1 liquid product that can be easily obtained from any carbon source, including biomass and CO2, has been proposed as a key component of such an anthropogenic carbon cycle in the framework of a "Methanol Economy". Methanol itself is an excellent fuel for internal combustion engines, fuel cells, stoves, etc. It's dehydration product, dimethyl ether, is a diesel fuel and liquefied petroleum gas (LPG) substitute. Furthermore, methanol can be transformed to ethylene, propylene and most of the petrochemical products currently obtained from fossil fuels. The conversion of CO2 to methanol is discussed in detail in this review.

Efficient synthesis of fluorescent-PET probes based on [¹8F]BODIPY dye.

We report the direct conversion of fluorescent probes to PET/fluorescent probes after efficient [(19)F]/[(18)F] exchange at the BODIPY motif. The radiolabeling of a NIR BODIPY dye was also established, which was conjugated with the RGD peptide for PET/fluorescence imaging of integrin expression in vivo.

Octahydriodo diborane (B2H8) and its protonated cations containing five-, six-, and seven-coordinate boron atoms.

Structures of octahydriodo diborane (B(2)H(8)) 1 and its protonated 3, diprotonated 5, triprotonated 6, and tetraprotonated 7 ions were found to be calculationally viable minima at the MP2/cc-pVTZ level of theory. Each structure contains two-electron three-center (2e-3c) bonds. The protonation of 1 to form 3 was found to be strongly exothermic by 176.0 kcal/mol. Subsequent protonation of 3 to form 5 was also found to be exothermic by 28.4 kcal/mol. Further protonation of 5 to form 6 was, however, computed to be endothermic by 122.0 kcal/mol whereas protonation of 6 to form 7 was again highly endothermic by 238.8 kcal/mol. Deprotonation barriers of the ions were also computed.

Synthesis and biological evaluation of fluorinated deoxynucleotide analogs based on bis-(difluoromethylene)triphosphoric acid.

It is difficult to overestimate the importance of nucleoside triphosphates in cellular chemistry: They are the building blocks for DNA and RNA and important sources of energy. Modifications of biologically important organic molecules with fluorine are of great interest to chemists and biologists because the size and electronegativity of the fluorine atom can be used to make defined structural alterations to biologically important molecules. Although the concept of nonhydrolyzable nucleotides has been around for some time, the progress in the area of modified triphosphates was limited by the lack of synthetic methods allowing to access bisCF(2)-substituted nucleotide analogs-one of the most interesting classes of nonhydrolyzable nucleotides. These compounds have "correct" polarity and the smallest possible steric perturbation compared to natural nucleotides. No other known nucleotides have these advantages, making bisCF(2)-substituted analogs unique. Herein, we report a concise route for the preparation of hitherto unknown highly acidic and polybasic bis(difluoromethylene)triphosphoric acid 1 using a phosphorous(III)/phosphorous(V) interconversion approach. The analog 1 compared to triphosphoric acid is enzymatically nonhydrolyzable due to substitution of two bridging oxygen atoms with CF(2) groups, maintaining minimal perturbations in steric bulkiness and overall polarity of the triphosphate polyanion. The fluorinated triphosphoric acid 1 was used for the preparation of the corresponding fluorinated deoxynucleotides (dNTPs). One of these dNTP analogs (dT) was demonstrated to fit into DNA polymerase beta (DNA pol beta) binding pocket by obtaining a 2.5 A resolution crystal structure of a ternary complex with the enzyme. Unexpected dominating effect of triphosphate/Mg(2+) interaction over Watson-Crick hydrogen bonding was found and discussed.

Air/Water-Stable Tridentate NHC-Pd Complex; Catalytic C-H Activation of Hydrocarbons via H/D Exchange Process in D(2)O.

While developing novel catalysts for carbon-carbon or carbon-heteroatom coupling (N, O, or F), we were able to introduce tridentate NHC-amidate-alkoxide palladium(II) complexes. In aqueous solution, these NHC-Pd(II) complexes showed high ability for C-H activation of various hydrocarbons (cyclohexane, cyclopentane, dimethyl ether, THF, acetone, and toluene) under mild conditions.

Ab initio/GIAO-CCSD(T) study of structures, energies, and 13C NMR chemical shifts of C4H7(+) and C5H9(+) ions: relative stability and dynamic aspects of the cyclopropylcarbinyl vs bicyclobutonium ions.

The structures and energies of the carbocations C 4H 7 (+) and C 5H 9 (+) were calculated using the ab initio method. The (13)C NMR chemical shifts of the carbocations were calculated using the GIAO-CCSD(T) method. The pisigma-delocalized bisected cyclopropylcarbinyl cation, 1 and nonclassical bicyclobutonium ion, 2 were found to be the minima for C 4H 7 (+) at the MP2/cc-pVTZ level. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level the structure 2 is 0.4 kcal/mol more stable than the structure 1. The (13)C NMR chemical shifts of 1 and 2 were calculated by the GIAO-CCSD(T) method. Based on relative energies and (13)C NMR chemical shift calculations, an equilibrium involving the 1 and 2 in superacid solutions is most likely responsible for the experimentally observed (13)C NMR chemical shifts, with the latter as the predominant equilibrating species. The alpha-methylcyclopropylcarbinyl cation, 4, and nonclassical bicyclobutonium ion, 5, were found to be the minima for C 5H 9 (+) at the MP2/cc-pVTZ level. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level ion 5 is 5.9 kcal/mol more stable than the structure 4. The calculated (13)C NMR chemical shifts of 5 agree rather well with the experimental values of C 5H 9 (+).

SYNTHESIS OF TRIFLUOROMETHYL-IMINES BY SOLID ACID/SUPERACID CATALYZED MICROWAVE ASSISTED APPROACH.

A new solid acid/superacid catalyzed microwave assisted synthesis of trifluoromethyl-imines is described. Various α,α,α-trifluoromethylketones react readily with primary amines to produce the corresponding imines. Two different strategies have been employed; one is the application of microwave irradiation coupled with solvent-free solid acid catalysis. The other method, for highly deactivated substrates includes the use of a pressure vessel at 175 °C temperature, with solid superacid catalysis. Using the solid acid K-10 montmorillonite or the superacidic perfluorinated resinsulfonic acid Nafion-H, a wide variety of trifluoromethylated imines have been synthesized using the above methods. The products have been isolated in good to excellent yields and high selectivities. This new environmentally friendly synthetic methodology provides significantly higher yields than traditional methods during relatively short reaction times for the preparation of the target compounds.

12/15-lipoxygenase inhibitors in diabetic nephropathy in the rat.

The 12/15-lipoxygenase (12/15-LO) pathway is activated in diabetes mellitus (DM), increasing 12(S)-hydroxyeicosatetraenoic acid (12-HETE). We showed that a 12-LO inhibitor, cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (CDC) inhibited 12/15-LO activity in vivo and assessed the efficacy of another 12/15-LO inhibitor, N-benzyl-N-hydroxy-5-phenylpentamidine (BHPP), to diminish urinary 12-HETE and ameliorate diabetic nephropathy (DN) over 4 months. Rats studied were control (C, n=8), DM (n=6), and rats injected with BHPP (C+BHPP, n=4) and (DM+BHPP, n=5). BHPP 3 mg/kg/day decreased urinary (U) 12-HETE/creatinine (cr) by 30-50% after one injection and after 1 week of daily injections in DM rats. U 12-HETE/cr excretion increased paradoxically in controls given BHPP. There was a highly significant relationship between U 12-HETE/cr excretion and U alb/cr (r=0.79, P<10(-5)), demonstrating that renal 12/15-LO pathway activation is associated with albuminuria. BHPP did not inhibit glomerular collagen synthesis or improve histology. More sustained 12-LO inhibition may improve albuminuria in DN.

Superelectrophilic protio methyl- and protio dimethylmethyleniminium dications.

Electronic structures and energies of superelectrophilic dications derived by protonation of methyl- and dimethylmethyleniminium (R'R' 'C=N+R'R' '; R', R' ' = CH3 or H) ions were calculated at the ab initio MP2/6-311+G level. The calculations identified the N-protonated isopropyleniminium dication 14 as a minimum structure. On the basis of computed energies, deprotonation energies of the global minimum structures were also calculated. The 13C NMR chemical shifts of the intriguing dication 14 were calculated using the GIAO-MP2 method. The 13C NMR chemical shifts of the isoelectronic analogue tert-butyl cation were also calculated at the same level in order to explore the effect of an additional charge in dications 14.

Efficient chemoselective carboxylation of aromatics to arylcarboxylic acids with a superelectrophilically activated carbon dioxide-Al(2)Cl(6)/Al system.

Aromatic carboxylic acids are obtained in good to excellent yield essentially free of diaryl ketones by carboxylation of aromatics with a carbon dioxide-Al(2)Cl(6)/Al system at moderate temperatures (20-80 degrees C). To optimize reaction conditions and study the reaction mechanism, experimental variables including temperature, amount of Al(2)Cl(6)/Al, various Lewis acids, role of metal additive, carbon dioxide pressure, etc. were studied. The carboxylation reaction was found to be stoichiometric rather than catalytic, with aluminum chloride forming a dichloroaluminate of carboxylic acids. Although the carboxylation takes place using AlCl(3) itself, the presence of metal additives, especially Al, increased the yield and selectivity of carboxylic acids. Because it was not possible to distinguish between two possible mechanistic pathways of the reaction on the basis of the experimental results, theoretical calculations using density functional theory (DFT) were also carried out. One possible pathway involves an initial complex between benzene and Al(2)Cl(6), with subsequent formation of organoaluminum intermediates (PhAlCl(2) and PhAl(2)Cl(5)). The other proceeds through the formation of various complexes of CO(2) with aluminum chloride (AlCl(3))(n), n = 1-4. The calculations have shown that the organometallic pathway, leading eventually through the formation of phenylaluminum dichloride, is endothermic by 33 kcal/mol. In contrast, the preferred CO(2)-AlCl(3) complex forms in an exothermic reaction (-6.0 kcal/mol) as does CO(2)AlCl(2)(+). On the basis of both experimental and calculational findings, the most feasible reaction mechanism proposed involves superelectrophilic aluminum chloride activated carbon dioxide reacting with the aromatics in a typical electrophilic substitution.

N6(2+) and N4(2+) dications and their n(12) and n(10) azido derivatives: DFT/GIAO-MP2 theoretical studies.

The structures and energies of N(6)(2+) and N(4)(2+) were calculated by using the density functional theory method at the B3LYP/cc-aug-pVTZ level. The C(2)(h)() symmetric form 1 and D(infinity)(h) form 5 were found to be the stable minima for N(6)(2+) and N(4)(2+), respectively. Dissociation of 1 into 5 and N(2) was computed to be endothermic by 25.1 kcal/mol. (15)N NMR chemical shifts and vibrational frequencies of 1 and 5 were also calculated. Interactions of 1 and 5 with azide ions were also probed representing N(12) and N(10).

Gitonic and distonic alkanonium dications (diprotonated alkane dications C(n)H(2n+4(2+)), n = 1-4)(1).

The structures and stabilities of gitonic and distonic alkanonium dications, i.e., diprotonated alkane dications C(n)H(2n+4)(2+) (n = 1-4), were investigated at the MP4(SDTQ)/6-311G**//MP2/6-31G** level. The global minimum energy structures (2, 4, 7, and 10) of the C(n)H(2n+4)(2+) dications are double C--H protonated alkanes to give structures with two two electron three-center (2e-3c) bonds. Two different dissociation pathways for the dications, viz deprotonation and demethylation, were also computed. Demethylation was found to be the favorable mode of dissociation.