Synthesis of Vinyl Sulfone 1,6-Enynes for [2+2+2] Cycloisomerization Methodology
Ron R. Ramsubhag1, Gregory B. Dudley2
1 - Department of Chemistry and Biochemistry, Florida State University, 102 Varsity Way, 5007 CSL, Tallahassee, FL 32306-4390, USA
1, 2 - Gregory B. Dudley - Eugene Bennett Department of Chemistry, 100 Prospect Street, 222 Clark Hall, West Virginia University, Morgantown, WV 26506-6045
1,6-Enynes have proven to be invaluable building blocks that has help innovate alkyne chemistry. Using the fragmentation/olefination methodology developed in our lab, we can now synthesize a new type of 1,6-enyne which incorporates a vinyl sulfone. Here, these vinyl sulfone enynes are used to explore and expand [2+2+2] cycloisomeriaztion methodology. Various alkynes are used as coupling partners to synthesize variety of gem-dimethyl indanes.
Facile Tuning of Atropisomeric P,N-Ligands Towards Enantioselective Conjugate Addition
Sourabh Mishra, Ji Liu, Aaron Aponick
Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611
Catalytic asymmetric conjugate addition reactions are very important tools for the assembly of chiral compounds and Meldrum’s acid derivatives are excellent acceptors for such transformations. Facile diversification of β–alkynyl adducts makes them highly useful targets and a new synthetic method using StackPhos, an imidazole–based atropisomeric P,N–ligand has been developed. Employing a ligand modification strategy, this transformation was achieved with a broad substrate scope and excellent enantioselectivity. Recent results using modified ligands will be presented, as well as the application of the method.
DESIGN AND SYNTHESIS OF HYDROGEN—BONDING CAPABLE 1,4-DIHYDROPYRAZINO[2,3-b]QUINOXALINE-2,3-DIONES FOR APPLICATIONS IN ORGANIC FIELD-EFFECT TRANSISTORS
Tural N. Akhmedov,1 Daken J. Starkenburg,2 Kyle J. Chesney,1 Jiangeng Xue,2 and Ronald K. Castellano1
1Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA
2Department of Materials Science and Engineering, University of Florida, P.O. Box 116400, Gainesville, FL 32611-6400, USA
Up and coming technology in π-conjugated organic field-effect transistors (OFETs) can in principle allow for cost-effective production of small scale electronics. In order to effectively compete with widely used inorganic materials such as silicon, field-effect transistors of organic origin must be properly tuned for good charge mobility. It is known that ordered π-π stacking among organic molecules is essential for efficient charge transport; however, the desired order is not always achieved. To be able to better control π-stacking arrangements in the solid state, introduction of heterocycles to the π-backbone capable of strong hydrogen -bonding has recently been shown to be a promising approach. Reported here is the synthesis of a family of electron deficient N-heteroacenes containing the H-bonding capable 1,4-dihydropyrazine-2,3-dione moiety towards improvement of charge carrier mobility in OFETs.
Synthesis of Ketene Dithioacetals
Jin Wang, Teng Yuan, Xiaodong Shi*
University of South Florida
ketene dithioacetals can be accessed using a gold-catalyzed reaction. Substrate scope, mechanism as well as synthetic applications of this transformation will be discussed.
ANALOG ORIENTED SYNTHESIS OF TERPENOID CORES: TOWARDS DOLESTANE AND PSEUDO-GUAIANOLIDE ARCHITECTURES
Fabien Emmetiere and Alexander J. Grenning
Department of Chemistry, University of Florida, Gainesville FL 32611-7200, USA
Terpene molecules are abundant in nature and a lot of them are relevant from a pharmaceutical standpoint. Unfortunately, the isolation of these terpenes remains very challenging since they must be extracted from living organisms allowing for no more than few milligrams to be recovered. In order to tackle this limitation, we have recently reported a simple and scalable methodology to access terpenoid cores using readily available reagents. Using this approach, simple cyclic ketones were converted to decorated 5-7 or 6-7 fused ring systems in only 4 steps. From these preliminary results, we were able to devise a strategy toward tricyclic natural products. Among them, dolestane and pseudo-guaianolide architectures are of particular interest in terms of synthetic challenges and potential latent biological activities. Recent results demonstrate that analogs of the targeted natural products can be synthesized.
Nucloephile assisted activation of diazonium salt for gold oxidation chemistry
S. Hosseyni, X. Shi,
University of South Floirda
The discovery of photo-assisted diazonium activation toward gold(I) oxidation greatly extended the scope of gold redox catalysis by avoiding the use of strong oxidant. Some practical issues that limit the applications of this new type of chemistry are the relative low efficiency (long reaction time and low conversion) and the strict reaction conditions control (degassing and inert reaction environment). An alternative, photo-free condition is developed through Lewis base activated diazonium activation. With this method, simple PPh3AuCl catalyst was used with the combination of NaHCO3 and diazonium salts to produce gold(III) intermediate. Effective activations of various substrates, including alkyne, alkene and allene have been achieved followed by gold(III) reductive elimination, giving the C-C bond coupling products with good to excellent yields
THIENYL-PYRIDYL BASED FUNCTIONAL OLIGOMERS: DESIGN, SYNTHESIS, AND POTENTIAL APPLICATIONS AS SENSORS
Lei Li,1 Asmerom O. Weldeab,1 Seda Cekli,1 Kirk S. Schanze,1,2 and Ronald K. Castellano1
1 Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA
2 Department of Chemistry, University of Texas at San Antonio, One UTSA Way, San Antonio, TX 78249, USA
Owing to their outstanding electronic and optical properties, π-conjugated oligomers containing the thienyl-pyridyl unit are promising candidates for optoelectronic applications. Reported here is the first chemical and photophysical evaluation of this unit in the context of extended Donor-Acceptor-Donor (D-A-D) π-conjugated oligomers. Two families with different internal electron acceptor structures (either isoindigo or diketopyrrolopyrrole) have been designed and synthesized, each featuring pyridine linked in its 4-position at the termini. The consequences of pyridyl protonation (i.e., the addition of trifluoroacetic acid) and metalation (i.e., the addition of Pd2+/Cu2+) on photophysical properties have been evaluated by UV-Vis and fluorescence spectroscopy using both the D-A-D oligomers and simplified model compounds. Additionally, 1H NMR studies have been carried out to assign the protonation and metalation positions.
Gold Redox Catalysis through Base Initiated Diazonium Decomposition toward Alkene, Alkyne, Allene and Cyclopropanol Activation
Boliang Dong, Haihui Peng, Seyedmorteza Hosseyni, Stephen E. Motika, Abiola A. Jimoh and Xiaodong Shi*
University of South Florida
The discovery of photo-assisted diazonium activation toward gold(I) oxidation greatly extended the scope of gold redox catalysis by avoiding the use of a strong oxidant. Some practical issues that limit the application of this new type of chemistry are the relative low efficiency (long reaction time and low conversion) and the strict reaction condition control that is necessary (degassing and inert reaction environment). Herein, an alternative photo-free condition had been developed through Lewis base induced diazonium activation. With this method, a unreactive Au(I) catalyst was used in combination with Na2CO3 and diazonium salts to produce a Au(III) intermediate. The efficient activation of various substrates, including alkyne, alkene, allene and cyclopropanol were achieved, followed by rapid Au(III) reductive elimination, which yielded the C-C bond coupling products with good to excellent yields. Relative to the previously reported photo-activation method, our approach offered a higher efficiency through faster reaction rates and provided significantly broader reaction scope.