Radical-induced reaction of monoiodo- and diiodo-perfluoroalkanes with allyl acetate: telomer and rearranged products, mass-spectral distinguishing of regioisomers (original) (raw)
J. Am.Chem.Soc. 1988, 110, 3247-3252.pdf
Acid-catalyzed rearrangement of 6-bromo-2,4-dimethyl-4-(phenylamino)cyclohexa-1 ,4-dienone (1, a quinamine) in aqueous methanol gives, from a so-called quinamine rearrangement, 4'-amino-6-bromo-2,4-dimethyldiphenyl ether (2) and a number of byproducts. The ratio of yield of 2 to that of byproducts is 76:24. The byproducts are, mostly, 1,3-dimethylcarbazole (7) and some of its derivatives, the relative yields of which depend on the concentration of the catalyzing acid, HCI. The major byproduct in low HC1 concentrations is 1,3-dimethyl-4-methoxycarbazole (9). Kinetic isotope effects (KIE) were measured for the formation of 2 from 1, which was labeled at the carbonyl oxygen atom (['*0]-1), the nitrogen atom ([I5N]-1), and the para position of the aniline ring ([4-I4C]-1). The KIE (averages) were as follows: k ( ' 6 0 ) / k ( 1 8 0 ) , 1.0399; k(I4N)/k(l5N), 1.0089; /~( ' * c ) / k (~~C ) , 1.0501. The results suggest that the formation of 2 is a concerted process, a [5,5]-sigmatropic rearrangement, and not a two-step one, going through the rate-determining formation of a r-complex. KIE were measured for the formation of both 2 and 9 from 1, which was labeled in the ortho position of the anilino ring ([2-14C]-1). The KIE [k(12C)/k(14C)] were respectively 0.9895 and 1.0697. These results suggest that the byproduct (9) is formed by a concerted process, too, a [3,3]-sigmatropic rearrangement to an intermediate , which continues on to 9 and the other byproducts. The results show also that 2 cannot be formed from 1 by a succession of two [3,3]-sigmatropic rearrangements, the first of which is to 14. Thus, the quinamine rearrangements. on the basis of our results with 1, appear to be concerted, rather than a-complex intermediate, processes.
Chemistry - A European Journal, 2009
The matrix isolation and spectroscopic characterization of two C 6 F 4 isomers, the perfluorinated o-benzyne 4 and the m-benzyne 5, is reported. UV photolysis of tetrafluorophthalic anhydride 6 in solid argon at 10 K results in the formation of CO, CO 2 , and 1,2didehydro-3,4,5,6-tetrafluorobenzene (4) in a clean reaction. On subsequent 350 nm irradiation 4 is carbonylated to give the cyclopropenone 7. 1,3-Didehydro-2,4,5,6-tetrafluorobenzene (5) was synthesized by UV irradiation of 1,3diiodo-2,4,5,6-tetrafluorobenzene (8) via 2,3,4,6-tetrafluoro-5-iodophenylradical 9. Photolysis of 8 in solid neon at 3 K produces good yields of both radical 9 and benzyne 5, while in argon at 10 K no reaction is observed. Thus, the photo-chemistry in neon at extremely low temperature markedly differs from the photochemistry in argon. The formation of 5 from 8 via 9 is reversible, and annealing the neon matrix at 8 K leads back to the starting material 8. The benzynes 4 and 5 and the radical 9 were characterized by comparison of their matrix IR spectra with density functional theory (DFT) calculations.
The Radical Cation ofanti-Tricyclooctadiene and Its Rearrangement Products
Chemistry - A European Journal, 2000
The anti dimer of cyclobutadiene (anti-tricyclo[4.2.0.0 2,5 ]octa-3,7-diene, TOD) is subjected to ionization by g-irradiation in Freon matrices, pulse radiolysis in hydrocarbon matrices, and photoinduced electron transfer in solution. The resulting species are probed by optical and ESR spectroscopy (solid phase) as well as by CIDNP spectroscopy (solution). Thereby it is found that ionization of anti-TOD invariably leads to spontaneous decay to two products, that is bicyclo[4.2.0]octa-2,4,7-triene (BOT) and 1,4-dihydropentalene (1,4-DHP), whose relative yield strongly depends on the conditions of the experiment. Exploration of the C 8 H 8
The Journal of Organic Chemistry, 2006
The photoinduced competitive rearrangements of 5-perfluoroalkyl-3-amino(N-alkylamino)-1,2,4-oxadiazoles have been investigated by DFT calculations and UV-vis spectroscopy. The observed product selectivity depends on the number of hydrogen atoms present in the amino moiety and involves two or three possible routes: (i) ring contraction-ring expansion (RCRE), (ii) internal-cyclization isomerization (ICI), or (iii) C(3)-N(2) migration-nucleophilic attack-cyclization (MNAC). UV absorption and fluorescence spectra of the reactants, and vertical excitation energy values, calculated by time dependent DFT, support the involvement of a neutral singlet excited state in the photoexcitation process. The values of the standard free energy of the most stable prototropic tautomers of reactant, products, proposed reaction intermediates, and deprotonated anionic transition states allowed us to rationalize the competition among the three rearrangements, in agreement with chemical trapping experiments, in terms of: (i) the evolution of the excited state toward three stable ground-state intermediates, (ii) tautomeric and deprotonation equilibria occurring in methanol solution for each intermediate, and (iii) relative stabilization of intermediates and transition states in the thermally driven section of the reaction. (1) (a) Diana, G. D.; Volkots, D. L.; Nitz, T. J.; Bailey, T. R.; Long, M. A.; Vescio, N.; Aldous, S.; Pevear, D. C.; Dutko, F. J. J. Med. Chem. 1994, 37, 2421-2436. (b) Saunders, J.; Cassidy, M.; Freedman, S. B.; Harley, E. A.; Iversen, L. L.; Kneen, C.; MacLeod, A. M.; Merchant, K. J.; Snow, R. Zheng, X.; Qian, L.; Ellis, C.; Cai, Z.-wei; Wautlet, B. S.; Mortillo, S.; Jeyaseelan, Sr., R.; Kukral, D. W.; Fura, A.; Kamath, A.; Vyas, V.; Tokarski, J. S.; Barrish, J. C.; Hunt, J. T.; Lombardo, L. J.; Fargnoli, J.; Bhide, R. S. J. Med. Chem. 2005, 48, 3991-4008. (d) Bokach, N. A.; Khripoun, A. V.; Kukushkin, V. Yu.; Haukka, M.; Pombeiro, A.
Journal of Fluorine Chemistry, 1993
acetates, R#ZH&HICHaOAc (1) (RF= i-C3F7, C,F,, C,F,,, CsF,7)r have been rearranged thermally to I-iodo-3-perlluoroalkyl-2-propyl acetates, R&H,CH(OAc)CH,I (Z), in 89% yield over the temperature range 120-200 "C. The results indicate that the rearrangement ls a reversible process which is shifted towards the formation of 2. The equilibrium regio isomer ratio (l/2 = 1:8) was independent of the temperature and of the nature of the RF substituent. It is proposed that the rearrangement proceeds through a free-radical mechanism Including 1,2migration of the acetoxy group after thermal scission of the C-I bond.
Journal of the American Chemical Society, 1981
This result is, however, entirely consistent with our calculations, which, as we have pointed out, predict that it should be much harder to trap the ketene intermediate (3b) from 5 than that (3a) from 4. The heat of formation of the transition state for dissociation of 3b (into 7) is lower by 7 kcal/mol than that for its formation from 2b, whereas in the case of 3a, both transition states are similar in energy. This difference is not unexpected because alkyl substituents stabilize carbenes. The conversion of 3b to 7 should therefore be more facile than that of 3a to 6. It would be of interest to try further trapping experiments under conditions where loss of thermal excitation might be expected to occur more readily than in our case. For example it should be possible to codeposit carbon atoms and 5 in a dilute argon matrix and then allow them to react by warming the matrix until it softens or melts. Summary and Conclusions The MNDO calculations reported here seem to suggest rather strongly that the deoxygenation of carbonyl compounds to carbenes by atomic carbon takes place by addition of carbon to the CO bond rather than by a direct electrophilic attack on oxygen, as has been commonly believed. The initial adduct, an oxiranylidene, rearranges to a ketene which undergoes decarbonylation by a "hot molecule" reaction, the necessary energy being provided by the extreme exothermicity of the two previous steps. When arcgenerated carbon atoms reacted with cold butanal, the intermediate ketene could be identified in the products by hydration to butyric acid. Experimental Section Reaction of Chemically Generated Carbon Atoms with 4 and 5. 5-Diazotetrazole (8) was prepared as described previously,"*'* and-0.1 mmol was coated as a thin film on the walls of a 500" round-bottom flask. The flask was evacuated and 100 mm of gaseous carbonyl compound was admitted. The flask was closed and 8 was decomposed by immersing it in a 100 OC oil bath for 5 min. The flask was then opened on a vacuum line and the contents analyzed. The products were analyzed
Journal of Fluorine Chemistry, 2001
The pyrolyses of 4-phenyl-2,3,5,6-tetra¯uorophenyl prop-2-enyl ether (26) under¯ash vapour phase (FVP) conditions at 3508C and of 4-tri¯uoromethyl-2,3,5,6-tetra¯uorophenyl prop-2-enyl ether (27) on heating in vacuo at 1698C give mixtures of products which include 3phenyl-2,4,5,7-tetra¯uorotricyclo[3.3.1.0 2,7 ]non-3-ene-6-one (28), and 3-tri¯uoromethyl-2,4,5,7-tetra¯uorotricyclo[3.3.1.0 2,7 ]non-3-ene-6one (31), respectively, the products of one of the two possible intramolecular Diels±Alder reactions of the Claisen rearrangement intermediates 2. FVP of 26 at 4308C and 27 at 4508C give the bicyclic compounds 7-phenyl-2,5b,6,7ab-tetra¯uoro-3ab,4,5,7atetrahydroinden-1-one (34) and 7-tri¯uoromethyl-2,5b,6,7ab-tetra¯uoro-3ab,4,5,7a-tetrahydroinden-1-one (37), respectively. It is proposed that these latter two compounds are formed via two possible intermediates produced by recyclisations of the tethered 2,4,5-tri¯uoro-3-(substituent)-2,4-cyclohexadienylmethyl¯uoroketene (23), itself formed via new retro-cyclisation reactions of 28 and 31, respectively. Also formed from 27 via 31 is 1,2,4b,5,7-tetra¯uoro-3-(tri¯uoromethyl)bicyclo[3.3.1]nona-2,6-dien-8-one (39). #
The Journal of Organic Chemistry, 1995
Rearrangement reactions of 15,16-epoxybeyeranes with acetoxy substituents at C-12 were carried out by treatment with ruthenium acetylacetonate. The stereochemistry of the acetoxy substituent group on C-12 decisively influences the process. In the case of the axial substituent, it aids in the stabilization of intermediate structures derived from an electron deficiency on (3-15 that allows the formation of 8(15-9)-abeo and 8(14-9),13(12-16)-diabeo compounds. This promotion of a positive charge on C-15 of the beyerene skeleton has not yet been explored in classical studies of rearrangements of tetracyclic diterpenes. The formation of some chlorinated compounds, produced by the solvent used (CHCld, was also observed in this process. When the starting product had a (2-12 acetoxy equatorial substituent, only migrations of the acetoxy group and some nucleophilic substitution processes were observed. The pathways of the rearrangements were proposed on the basis of findings obtained from rearrangement of C-12 deuterium labeled substrates.