Improvements have been made in the use of acylated pyridinium ylides for the transformation of 2methyl-l,4-naphthoquinone into derivatives (1 5) and (1 6) of naphtho[2,3-c] pyran-5,l O-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-9,1 O-diones such as (20a). If the leaving group is nuclear bromine as in 2-bromo-3-methyl-l,4-naphthoquinone, another reaction with 2 mot 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,l O-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.A small but significant group of natural products is based upon the naptho[2,3-c]pyran nucleus and contains members with antitumour and/or antibacterial activities2 We have improved and extended the route to such compounds from naphthoquinones and pyridinium y l i d e ~, ~ and found that it can be extended to regiospecific syntheses of acylated anthraquinones similar to antibiotic X-1488 1 C (Streptomyces) and altersolanol B4 and related to some of the highly physiologically active naphthacene quinones.' Results and DiscussionPaper 9/04753K

The 2‐alkylnaphthoquinones (I) react with pyridinium ylides, e.g. (IV) or their precursors (II) to form 3‐aroyl‐naphthoquinones (III) and (V).