76048-46-9Relevant academic research and scientific papers
Spirans. Part 13. The Synthesis and Orientation of Spirans related to Abel's Ketone (Naphthofuran-2(1H)-spiro-1'(2'H)-naphthalen-2'-one)
Dean, Francis M.,Herbin, G. Antonio,Matkin, David A.,Price, Anthony W.,Robinson, Malcolm L.
, p. 1986 - 1993 (2007/10/02)
The aryl substituents in the stereoisomers (2) and (3) of 1-phenylnaphthofuran-2(1H)-spiro-1'(2'H)-naphthalen-2'-one are subject to hindered rotation by an energy barrier of ca. 15 kcal mol-1.If the phenyl substituent carries an ortho substituent, however, rotation is prevented at temperatures up to 60 deg C (the highest examined): only one rotamer is obtainable (the other is too crowded) and it has the ortho-substituent cisoid with respect to the triarylmethine proton. The temperature-variable broadening of the signals from the protons of the aryl substituent serves to identify these in the 1H n.m.r. spectra.Some other resonances can be regularly identified by combinations of coupling constants, double-irradiation experiments, and shifts induced by using benzene instead of trichloromethane as sovent, but the only one of value for determining the configuration at the triarylmethine centre is that already known, i.e. the upfield shift in the resonance of the vinylic (3') proton caused by the aryl substituent when this lies immediately below it.A less precise but more general test of configuration is afforded by the mutual shielding of the aryl substituent and ring E when these are in adjacent planes. Methods of preparation are given for several related spirans, especially those containing the spiro-1'(4'H)-naphthalen-4'-one nucleus, and n.m.r. methods used to establish the configurations.
Spirans. Part 12. Stereochemical Control in the Oxidative Cyclisation of Bisnaphthols
Bennett, David J.,Dean, Francis M.,Herbin, G. Antonio,Matkin, David A.,Price, Anthony W.,Robinson, Malcolm L.
, p. 1978 - 1985 (2007/10/02)
Almost all oxidising agents cyclise benzylidene-1,1'-bis-2-naphthol (1a) to the stereoisomers (2a) and (3a) of phenylnaphthofuran-2(1H)-spiro-1'(2'H)-naphthalen-2'-one.A few are stereospecific.Hypobromite and persulphate give (2a), whereas iodine oxyacids and (diacetoxyiodo)benzene are specific for (3a).Radical-type oxidants such as hexacyanoferrate(III) and 2,4-di-t-butyl-6-phenylphenoxyl (4) give mixtures.Horseradish peroxydase behaves like hexacyanoferrate(III).The presence in the benzylidene residue of methoxy, nitro, fluoro, and other groups has little effect upon the isomer ratios, which are believed to be determined mainly by the bulk of the benzylidene group and the limits it imposes upon conformations during the oxidation processes.Oxidation by (diacetoxyiodo)benzene occurs through a cyclic intermediate (9) and gives the less-hindered (3a); oxidation of hypobromite occurs not directly but by exchange through an aryl hypobromite (Scheme) which halogenates its opposite naphthol nucleus and then substitutes the halogen, with inversion, thus leading to the more-hindered isomer (2a).
