17935-66-9Relevant academic research and scientific papers
THE BEHAVIOR OF THE SINGLET AND TRIPLET SPIN STATES OF METHYLENE-BRIDGED 1,8-NAPHTHOQUINODIMETHANE WITH O2
Pagni, Richard M.,Burnett, Michael N,,Hassaneen,Hamdi M.
, p. 843 - 851 (1982)
It has been shown that thermolysis of naphthocyclopropane 8 yields the singlet 1,8-naphthoquinodimethane 7 by disrotatory ring opening.In fluid solution the singlet biradical prefers to ring close to regenerate the starting material rather than under a 1,2-hydrogen shift to yield phenalene (9).It has been demonstrated that the singlet 7 does not react with O2 or undergo intersystem crossing to ground state triplet 7.It has also been shown by an intricate set of experiments that triplet 7 is produced on photolysis of 8 and that it reacts with O2.Unfortunately, it was not possible to elucidate unequivocally the mechanism by which triplet 7 reacts with O2.
Oligosaccharide analogues of polysaccharides. Part 19. Synthesis of 2- (naphthalen-1-yl)ethyl cellooligoglycosides and [(naphthalene-1,8- diyl)di(ethane-2,1-diyl)] bis[cellooligoglycosides]
Xu, Jinwang,Vasella, Andrea
, p. 1728 - 1752 (2007/10/03)
Glucosyl, cellobiosyl, cellotriosyl, cellotetraosyl, and cellooctaosyl residues were attached to naphthalene-1,8-diethanol (3) with the goal of preparing mimics of cellulose I. Among the templates that were considered, 1,8-diethynylnaphthalene (1) led to unstable products, and glycosidation of naphthalene-1,8-dimethanol (2) gave orthoesters that could not be rearranged to glycosides (Scheme 1). The conformation of 3 in the crystal and of its dimethyl ether 14 in solution was studied by X-ray analysis and force-field calculation (Figs. 1-3). Rotation around the Ar-CH2 and CH2-CH2 bonds of 14 is only weakly hindered and the O···O distance of crystalline 3 (6.01 A) corresponds to the mean distance of the parallel chains of cellulose I(β). The acetylated glycosyl bromides 18 and 19 were prepared by a new convergent synthesis (Scheme 2). Glycosylation of 3 by the glycosyl bromides 15-19 under established conditions of the Koenigs-Knorr reaction proved problematic, particularly on account of an acetyl transfer blocking one of the hydroxyethyl groups. Basic zinc carbonate, however, promoted glycosylation of 12 and 3 by the glycosyl bromides 15-19 and did not lead to transacetylation (Scheme 3). The mono- to tetrasaccharides 32-35 and 42-45 were isolated in yields of 5682%, and the octasaccharides 36 and 46 in 32 and 16%, respectively. The mono- and disaccharides 32, 33, 42, and 43 were deacetylated with NaOMe in MeOH. Aqueous NaOH was used for the tri-, tetra-, and octasaccharides 34-36 and 44-46, as their partially deacetylated derivatives proved insoluble in MeOH. The fully deprotected saccharides 37-41 and 47-50 were isolated in over 90%, while the yield of the dioctaoside 51 was lower on account of its poor water solubility.
1,4-Perinaphthadiyl. Singlet- and Triplet-State Reactivity of a Conjugated Hydrocarbon Biradical
Burnett, Michael N.,Boothe, Richard,Clark, Ernest,Gisin, Markus,Hassaneen, Hamdi M.,et al.
, p. 2527 - 2538 (2007/10/02)
1,4-Perinaphthadiyl (b) was generated from the azo precursor 1 by thermal elimination of nitrogen as well as by direct and sensitized photolysis.The biradical was persistent but light sensitive at low temperature in the triplet ground state (3b) and was characterized by optical and ESR spectroscopy; kinetic and spectrographic flash photolysis was used to monitor 3b at room temperature as a transient intermediate yielding naphthocyclobutane (2), divinylnaphthalene (3), and dimers (9,10).The lifetime of 3b was reduced from τ=0.2 ms in degassed solution to 0.2 μs in air-saturated solution, and as a result, peroxides (4, 6) were formed at the expense of the hydrocarbon products.However, the dependence of the peroxide yield on oxygen pressure required that a second intermediate also interacted with oxygen.This was identified as the singlet state of b undergoing catalyzed intersystem-crossing (ISC) upon diffusional encounter with triplet oxygen; its lifetime at 300 K was estimated as 1 ns, and the energy difference between 1b and 3b as 5 kcal/mol.The efficiency of spontaneous ISC from 1b to 3b was found to increase with decreasing temperature, and the yields of the different final products (2-4, 6, 9, 10) were strongly influenced by the conditions chosen for the formation of the biradical.The chemical properties of b are strikingly different from those of the related 1,3-perinaphthadiyls c and d due to the much shorter intrinsic lifetime of 1c and 1d.
