18259-45-5Relevant academic research and scientific papers
EPR, ENDOR and TRIPLE Resonance Characterization of Three Paramagnetic Redox Stages of 5-Methylene-5H-dibenzocycloheptene
Franco, M. Luisa T. M. B.,Lazana, M. Celina R. L. R.
, p. 3273 - 3280 (1994)
Radical anions and radical trianions derived from 5-methylene-5H-dibenzocycloheptene 1, 10-deuterio-5-methylene-5H-dibenzocycloheptene 1d and 5-dideuteriomethylene-5H-dibenzocycloheptene 1d2 by reduction with lithium, sodium, potassium and caesium in ethereal solvents have been studied by EPR, ENDOR and TRIPLE resonance spectroscopy.The spin and charge distribution in 1.(1-) and 1.(3-) are discussed both in terms of HMO-McLachlan and INDO calculations.The energies of the lowest unoccupied molecular orbital (LUMO) and of the next lowest unoccupied molecular orbital (NLUMO) are influenced differently by the strong interaction of the supercharged radical trianion with the counter-cations.A change in the orbital sequence of LUMO and NLUMO was predicted theoretically for the radical trianion relative to that found for the radical anion, in accordance with the experimental results.The radical cations 1.(1+), 1d.(1+) and 1d2.(1+) obtained via oxidation by AlCl3 in dichloromethane solution were also studied by EPR, ENDOR and TRIPLE resonance spectroscopy.The experimental results were also interpreted in terms of HMO-McLachlan and INDO methods.
Substituted 9-Anthraldehydes from Dibenzocycloheptanol Epoxides via Acid-Catalyzed Epoxide Opening/Semipinacol Rearrangement
Phumjan, Tanawat,Songthammawat, Poramate,Jongcharoenkamol, Jira,Batsomboon, Paratchata,Ruchirawat, Somsak,Ploypradith, Poonsakdi
, p. 13322 - 13349 (2021/09/13)
Starting from benzaldehyde derivatives, the corresponding dibenzocycloheptenol could be prepared in five steps. Under both substrate (secondary vs tertiary alcohol and the substituents on the aromatic ring(s)) and condition control, the subsequent epoxidation and acid-catalyzed epoxide opening/semipinacol rearrangement/aromatization afforded the corresponding 9-anthraldehydes in good yields, up to 88% over two steps. The presence of the electron-withdrawing group(s) on the aromatic ring(s) suppressed the rate of the epoxidation while the subsequent semipinacol rearrangement step required heating; the presence of the electron-donating group(s), on the other hand, frequently led to the decomposition during the epoxidation. From the mechanistic studies, the semipinacol rearrangement of the epoxide could precede the ionization at the bisbenzylic position, yielding the aldehyde intermediate. The ensuing dehydrative aromatization led to the formation of 9-anthraldehyde. Conversely, nucleophilic addition to the aldehyde and dehydrative aromatization with concomitant loss of formic acid led to anthracene.
Conformational analysis of some 5-substituted 5H-dibenzo[a,d]-cycloheptenes
Hjelmencrantz, Anders,Friberg, Annika,Berg, Ulf
, p. 1293 - 1300 (2007/10/03)
Conformations and inversion barriers of 5H-dibenzo[a,d]cycloheptene (1a), 5-amino-5H-dibenzo[a,d]cycloheptene (1b), 5-chloro-5H-dibenzo[a,d]cycloheptene (1e), 5-hydroxy-5H-dibenzo[a,d]cycloheptene (1d), 5-methyl-5H-dibenzo[a,d]cycloheptene (1f), N-benzyl-5H-dibenzo[a,d]cyclohepten-5-imine (2) and N-(5H-dibenzo[a,d]cyclohepten-5-yl)benzylideneamine (1c) have been studied by means of dynamic nuclear magnetic resonance spectroscopy (DNMR) techniques, and comparison of the experimentally derived thermodynamic parameters was made with MM3, PM3 and ab initio calculated results. Attempts to determine the inversion barrier of 3-isopropyl-5H-dibenzo[a,d]cyclohepten-5-one (3) failed.
Ritter Reactions. IX. Transannular Addition of Nitriles to the 5H-Dibenzocycloheptene Ring System
Pich, Kim C.,Bishop, Roger,Craig, Donald C.,Scudder, Marcia L.
, p. 837 - 852 (2007/10/02)
The 5H-dibenzocyclohepten-5-ols (1a-e) undergo sequential intramolecular and conventional Ritter reactions with acetonitrile to afford the cyclohepten-11-yl>acetamides (6a-e).Typical yields for these one-flask conversions are 52-64percent, except for the reaction of (1a) where production of the dimeric substance (4a) is favoured.Alcohol (1a) can provide either type of product in good yield, depending on the conditions employed, when reacted with benzonitrile.The molecular skeleton present in the adducts (6) has been confirmed by determination of the crystal structure of (6c) , a 9.188(3), b 14.632(5), c 16.563(9) Angstroem, α 115.64(9), β 90.92(2), γ 96.29(2) deg, Z 4, R 0.043>.
Excited-State Carbon Acids. Facile Benzylic C-H Bond Heterolysis of Suberene on Photolysis in Aqueous Solution: A Photogenerated Cyclically Conjugated Eight ? Electron Carbanion
Budac, David,Wan, Peter
, p. 887 - 894 (2007/10/02)
The possibility of excited-state carbon acid behavior of the dibenzylic protons of several dibenzannelated systems related to suberene (1) has been investigated in aqueous solution and in several organic solvents.It was found that only suberene (1) displayed observable excited-state carbon acid behavior.Thus photolysis of 1 in D2O-CH3CN solutions resulted in facile exchange of the benzylic protons with deuterium from D2O.Extended photolysis resulted in incorporation of two deuteriums at the benzylic position.Quantum yields for initial deuterium incorporation are in the range 0.02-0.03 for 1 in D2O-CH3CN solutions.Deuterium exchange from the benzylic position with solvent protons was also observed on photolysis of 5,5-dideuterio-5H-dibenzocycloheptene (2), where each deuterium atom was exchanged with solvent H2O in a sequential manner.Fluorescence quenching by water (in CH3CN solution) of the exchanging suberene systems (1 and 2) gave linear Stern-Volmer plots, with kq = (1.68 +/- 0.08) * 1E8 M-1 s-1 for 1 and (0.61 +/- 0.06) * 1E8 M-1 s-1 for 2, which corresponds to an isotope effect for quenching by water, (kH/kD)q = 2.8 +/- 0.4.Fluorescence titration of 1 and 11 as a function of medium acidity gave an estimate of pK(S1) ca. -1 for these carbon acids.This compares to their estimated pK(S0) ca. 31-38.
Synthesis of (5R,10S,11R)-(+)-10,11-Dihydro-5-methyl-5H-dibenzocyclohepten-5,10-imin-11-ol: A Hydroxylated Metabolite of MK-0801
Larsen, Robert D.,Davis, Paul,Corley, Edward G.,Reider, Paul J.,Rothauser Lamanec, Theresa,Grabowski, Edward J. J.
, p. 299 - 304 (2007/10/02)
Two approaches to the synthesis of the MK-0801 metabolite, (5R,10S,11R)-(+)-10,11-dihydro-5-methyl-5H-dibenzocyclohepten-5,10-imin-11-ol (1a), from dibenzosuberenone (2) are presented.Selective ring opening of an aziridine with acetyl bromide and inversion of the stereochemistry provide 1a.Alternatively, formation of an oxazolidinone ring at the 10,11-position of the suberenone via a bromohydrin (9) is followed by acid-catalyzed cyclization of the oxazolidinone-carbinol 12 to provide 1a.A practical resolution for obtaining the active 5R,10S,11R-(+) enantiomer is described.
Contrasting Photosolvolytic Reactivities of 9-Fluorenol vs 5-Suberenol Derivatives. Enhanced Rate of Formation of Cyclically Conjugated Four ? Carbocations in the Excited State
Wan, Peter,Krogh, Erik
, p. 4887 - 4895 (2007/10/02)
The photosolvolysis of 9-fluorenol (1) and several of its derivatives, as well as related systems, has been studied in aqueous methanol and acetonitrile solutions.The primary aim of this study was to examine the effect of the internal cyclic array (ICA) of these compounds in promoting photosolvolysis with respect to the number of ? electrons available in the ICA.It was observed that 9-fluorenol derivatives photosolvolyze much more efficiently than any of the related systems studied in this work.In contrast, ground-state 9-fluorenol derivatives are the least reactive systems with respect to solvolysis.Quantum yields for methyl ether formation for photosolvolysis in 50percent MeOH-H2O are reported for 1-3.Rate constants for solvent-assisted photodehydroxylation (ks) are calculated on the basis of the proposed mechanism of heterolytic C-OH bond rupture in the primary photochemical step and are in the range (1.3-1.6)x1E10 s-1 for 1-3.
