15963-46-9Relevant academic research and scientific papers
Bridgehead substituents effect on the reactivity of bicyclobutane in its reactions with nucleophiles. A comparison with olefinic systems
Azran, Carmela,Hoz, Shmaryahu
, p. 11421 - 11430 (1995)
The reactivity of bridgehead substituted bicyclobutanes towards nucleophilic attack was compared with that of the analogous vinylic compounds. Ab initio calculations suggest that the substituents exert nearly the same energetic effects on the ground state of the two systems. The observed difference in the reactivity of the two systems stems, therefore, from the different nature of corresponding transition states.
Selective C?H Halogenation with a Highly Fluorinated Manganese Porphyrin
Li, Gang,Dilger, Andrew K.,Cheng, Peter T.,Ewing, William R.,Groves, John T.
, p. 1251 - 1255 (2018)
The selective C?H functionalization of aliphatic molecules remains a challenge in organic synthesis. While radical chain halogenation reactions provide efficient access to many halogenated molecules, the use of typical protocols for the selective halogenation of electron-deficient and strained aliphatic molecules is rare. Herein, we report selective C?H chlorination and fluorination reactions promoted by an electron-deficient manganese pentafluorophenyl porphyrin catalyst, Mn(TPFPP)Cl. This catalyst displays superior properties for the aliphatic halogenation of recalcitrant, electron-deficient, and strained substrates with unique regio- and stereoselectivity. UV/Vis analysis during the course of the reaction indicated that an oxo-MnV species is responsible for hydrogen-atom abstraction. The observed stereoselectivity results from steric interactions between the bulky porphyrin ligand and the intermediate substrate radical in the halogen rebound step.
Prediction and Experimental Verification of the Stereoselective Electrocyclization of 3-Formylcyclobutene
Rudolf, Klaus,Spellmeyer, David C.,Houk, K. N.
, p. 3708 - 3710 (1987)
3-Formylcyclobutene has been synthesized from cyclobutene-1, 1-dicarboxylic acid; it opens at 25-70 deg C with an activation energy of 27 +/- 1 kcal/mol to give exclusively (> 98percent) the Z product, in accord with predictions.
Expedient synthesis of cis- and trans-3-aminocyclobutanecarboxylic acids
Radchenko, Dmytro S.,Tkachenko, Anton,Grygorenko, Oleksandr O.,Komarov, Igor V.
, p. 1644 - 1649 (2011/06/23)
An expedient approach to cis- and trans-3-aminocyclobutanecarboxylic acids was developed starting from 1,1-cyclobutanedicarboxylic acid. Stereochemistry of the title compounds was established by nuclear Overhauser effect spectroscopy experiments.
Atomic motions and protonation stereochemistry in nucleophilic additions to bicyclobutanes
Hoz, Shmaryahu,Azran, Carmela,Sella, Ariel
, p. 5456 - 5461 (2007/10/03)
Several nucleophilic reactions on bicyclobutanes activated at the gehead carbon by electron withdrawing groups (SO2Ph, CO2Me, COPh, and CN) were performed in MeOH. In all cases, the less stable 1,3-disubstituted cyclobutanes isomer was preferentially obtained (compared to the equilibrium ratio). The results for the two charge localizing groups CN and SO2Ph oppose the existing knowledge regarding the protonation stereochemistry of such carbanions. Ab initio calculations (6-31G*) have shown that as the nucleophile approaches the bicyclobutane, the bridgehead activating group moves inward toward an axial position. With a charge localizing group (CN and S(H)SO2) the carbanion remains pyramidal, whereas with C(H)=O as an activating group, the carbanion is nearly planar. It is suggested therefore that under conditions where the carbanion undergoes rapid protonation, it is trapped in its initial pyramidal geometry. Whereas, in cases where the lifetime of the carbamon is long enough to allow appreciable equilibration, protonation may result in a different product distribution. This hypothesis was tested by slowing down the protonation rates. As a result, the more stable isomer was indeed preferentially obtained.
SYNTHESIS OF SQ-32,829, A NEW NUCLEOSIDE ANTIVIRAL AGENT
Jacobs, G. A.,Tino, J. A.,Zahler, R.
, p. 6955 - 6958 (2007/10/02)
The guanine-containing cyclobutane nucleoside analog SQ-32,829 (1) was synthesized in 8 steps from 1,1-cyclobutanedicarboxylic acid(3).
An Electron Spin Resonance Study of Pentadienyl and Related Radicals: Homolytic Fission of Cyclobut-2-enylmethyl Radicals
Davies, Alwyn G.,Griller, David,Ingold, Keith U.,Walton, John C.,Lindsay, David A.
, p. 633 - 641 (2007/10/02)
Pentadienyl radicals were generated from penta-1,4-diene and cis and trans-1-bromopenta-2,4-diene, and were observed in the E,E (1) and E,Z (2) conformations in hydrocarbon solution by e.s.r. spectroscopy.The E,Z-radicals are converted into the E,E-radicals at T > ca.170 K, but the E,E-radicals are not converted into the E,Z-radicals in the accessible temperature range.From the estimated barrier to rotation in E,Z-pentadienyl radicals the methane based stabilization energy (E8Me-H) was estimated to be 104 kJ mol-1.Pentadienyl radicals can also be obtained from ring-opening of cyclobut-2-enylmethyl radicals (3).Bromine abstraction from cyclobut-2-enyl methyl bromide by triethylsilyl radicals gave cyclobut-2-enylmethyl radicals at temperatures below ca.230 K.Above this temperature homolytic fission of the cyclobutene ring occured and pentadienyl radicals in the E,E-conformation were detected by e.s.r.Initially,E,Z-pentadienyl radicals must be formed, but at the temperature of ring fission these are converted into the E,E-radicals and so are not observed.Hydrogen abstraction from neither 3-methylcyclobutene nor from bicyclopentane yields (3) : instead 3-methylcyclobutenyl radicals and cyclopent-3-enyl radicals are formed, respectively.E.s.r.parameters are also reported for a range of substituted pentadienyl radicals generated from the corresponding 1,4-dienes.Of these radicals only 3-trimethylsiloxypentadienyl was observed in two conformations.
