- Pyridinium Ylides in Syntheses of Naphthopyrandiones and in Regioselective Syntheses of Acylated Anthraquinones Related to Fungal and Bacterial Metabolites
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Improvements have been made in the use of acylated pyridinium ylides for the transformation of 2-methyl-1,4-naphthoquinone into derivatives (15) and (16) of naphthopyran-5,10-dione, containing furan and thiophene groups.The substitution and cyclisation steps can be combined effectively by using 2-phenoxymethyl- instead of 2-methyl-naphthoquinone.The use of better leaving groups than phenoxy (especially 4-nitrophenoxy) allows the quinone to react with two proportions of ylide and leads regiospecifically to 1-aroyl-2-arylanthracene-9,10-diones such as (20a).If the leaving group is nuclear bromine as in 2-bromo-3-methyl-1,4-naphthoquinone, another reaction with 2 mol equiv. of ylide leads to complex red intermediates of type (31) which in contact with alumina are quantitatively converted into the regioisomeric 2-aroyl-3-arylanthracene-9,10-diones such as (22a).The structures have been determined by standard methods but special features of the NMR spectra are reported including a case of extreme line broadening by traces of iron.Mechanisms are suggested for the diverse reactions between the quinones and the ylides.
- Aldersley, Michael F.,Chishti, Shuhid H.,Dean, Francis M.,Douglas, Mark E.,Ennis, David S.
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p. 2163 - 2174
(2007/10/02)
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