Radical-induced reaction of monoiodo- and diiodo-perfluoroalkanes with allyl acetate: telomer and rearranged products, mass-spectral distinguishing of regioisomers (original) (raw)
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Mechanisms of the Intriguing Rearrangements of Activated Organic Species
2003
Abbreviations and symbols ix Word Count xiii Chapter 1: Introduction 1 1.1 Aims of this thesis 2 1.2 A review of the mechanism of the β-acyloxyalkyl radical rearrangement 2 1.3 The β-trifluoroacetoxyalkyl radical rearrangement 14 1.4 Other isomerisations which may share the same mechanism: The rearrangement of N-alkoxy-2(1H)-pyridinethiones 16 1.5 References 19 Chapter 2: Kinetics of the β−trifluoroacetoxyalkyl radical rearrangement 23 2.1 Introduction 24 2.2 A review of β-acyloxyalkyl radical rearrangement kinetics 24 2.3 The search for a suitable system for study 31 2.3.1 2-Trifluoroacetoxy-1-hexyl radical 31 2.3.2 Reaction of β-bromoester 2.50 with Bu 3 SnH 32 2.3.3 A faster rearrangement 34 2.3.4 Reaction of β-bromoester 2.59 with Bu 3 SnH 34 2.4 Determination of the equilibrium constant 34 2.4.1 Theory 35 xv 2.4.2 Preparation of β-bromoester 2.66 36 2.4.3 Reaction of β-bromoester 2.66 with Bu 3 SnH 37 2.5 Kinetics experiments 38 2.5.1 The kinetic scheme and analytical method 38 2.5.2 Conducting the kinetic experiments and product analysis 41 2.5.3 Management of analytical complexities 43 2.5.4 Kinetics results 46 2.6 Discussion of results 53 2.7 Conclusions 57 2.8 Experimental 58 2.9 References 72 Chapter 3: A labelled-oxygen study of the regiochemistry of the β-trifluoroacetoxyalkyl radical rearrangement 74 237 5.3.7 Attempted detection and isolation of intermediates 239 5.3.7.1 Addition of a radical scavenger 239 5.3.7.2 Esr spectroscopy 240 5.3.7.3 Cyclic voltammetry 241 5.3.7.4 Isolation and attempted identification of intermediates 244 5.4 Conclusions 247 5.5 Future work 249 5.6 Experimental 250 5.7 References 277 Chapter 6: General discussion and conclusions 284 6.1 Introduction 285 6.2 The β-trifluoroacetoxyalkyl radical rearrangement 285 6.2.1 What is known about the rearrangement of the 2-methyl-2-trifluoroacetoxy-1-heptyl radical? 285 6.2.2 Migrating group electronic effects 287 6.2.3 Relationship between rearrangement regiochemistry and kinetics 288 6.2.4 Is the regiochemistry controlled by the conformation of the ester group? 289 6.2.5 Predicted dynamics for a radical ion pair intermediate
The Journal of Organic Chemistry, 1991
2 3 31 c -0 20000 40000 60000 60000 101 1.79, 1.03, 0.67 Hz, 1 H), 5.65 (dddd, J = 15.41, 0.76, 0.68,0.67 Hz, 1 H), 5.99 (dddd, J = 15.41, 10.13, 1.03,0.55 Hz, 1 H), 6.29 (dddd, J = 16.92, 10.13, 10.11, 0.68 Hz, 1 H). Acknowledgment.
The Journal of Organic Chemistry, 2009
The photoinduced reactions of o-iodoanilides (o-IC 6 H 4 N(Me)COR, 4a-d) with sulfur nucleophiles such as thiourea anion (1,-SCNH(NH 2)), thioacetate anion (2, MeCOS-), and sulfide anion (3, S 2-) follow different reaction channels, giving the sulfides by a radical nucleophilic substitution or the dehalogenated products by hydrogen atom transfer pathways. After an initial photoinduced electron transfer (PET) from 1 to iodide 4, the o-amide aryl radicals 12 are generated. These aryl radicals 12 afford alternative reaction pathways depending on the structure of the R-carbonyl moiety: (a) 12b (R) Me) adds to 1 to render the methylthio-substituted compounds by quenching the thiolate anion intermediate with MeI after irradiation; (b) 12c (R)-CH 2 Ph) follows a 1,5-hydrogen transfer to give a stabilized R-carbonyl radical (17); and (c) 12d (R) t-Bu) affords 1,6-hydrogen transfer, followed by a 1,4-aryl migration to render an amidyl radical (20), which is reduced to the N-benzyl-N,2-dimethylpropanamide (10). Together with this last rearranged product, the ipso substitution derivative was also observed. Similar results were obtained in the PET reactions of 4d (R) t-Bu) with anions 2 and 3 under entrainment conditions with the enolate anion from cyclohexenone (5) or the tert-butoxide anion (6). From this novel rearrangement, and only under reductive conditions by PET reaction with anion 5, iodide 4d (R) t-Bu) affords quantitatively the propanamide 10. The energetic of the intramolecular rearrangements followed by radicals 12b-d were rationalized by B3LYP/6-31+G* calculations.
Stereochemistry. 83. Unusual rearrangements in cage compounds due to proximity effects
The Journal of Organic Chemistry, 1993
The strained keto diol 5 underwent an unexpected rearrangement in the presence of HzO-TEA-CHsCN at 20 O C to afford two isomeric products 6 and 7. The latter two compounds undergo further conversion to carboxy keto diol 8. The structures of 6-8 were elucidated by heterero COSY experiments and in the case of 6 by X-ray diffraction. The transformation of 5 to 6 and 7 is interpreted as involving an unusual retroaddition of a benzylic anion to a cyclobutanone 5-40. This is facilitated by subsequent readdition of this anion to another proximally located ketone with formation of a cyclopropanol 11, which is immediately converted to 6 and 7.
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.