Process for the preparation of 5-(substituted)-10 methoxy-2,2,4-trimethyl-2,5-dihydro-1H-chromeno [3,4-F] quinolines and derivatives thereof

A process for the preparation of 9,10-dihydroxy-2,2,4-trimethyl-1,2-dihydro-5H-chromeno[3,4-f]quinolin-5-one, comprising the steps of:

• (a) treating a compound selected from the group consisting of 2-bromo-1,3,4-trimethoxybenzene, 2-iodo-1,3,4-trimethoxybenzene and 1,2,4-trimethoxybenzene with an organolithium reagent in a first solvent, followed by addition of ZnCl2, followed by addition of a compound selected from the group consisting of methyl 2-bromo-5-nitrobenzoate, methyl 2-iodo-5-nitrobenzoate and methyl 5-nitro-2-{[(trifluoromethyl)sulfonyl]oxy}benzoate, followed by addition of a first transition metal catalyst to provide methyl methyl 2′,3′,6′-trimethoxy-4-nitro-1,1′-biphenyl-2-carboxylate;
• (b) treating said methyl 2′,3′,6′-trimethoxy-4-nitro-1,1′-biphenyl-2-carboxylate with tribromoborane in a second solvent to provide 1,2-dihydroxy-8-nitro-6H-benzo[c]chromen-6-one;
• (d) treating said 1,2-dihydroxy-8-nitro-6H-benzo[c]chromen-6-one with a second transition metal catalyst under a hydrogen atmosphere at a pressure of about 20 psi to about 60 psi in a third solvent wherein said third solvent is N-methylpyrrolidin-2-one at a concentration of about 0.5M to about 1.0M;
• and
• (e) treating the product of step (d) with acetone and iodine in a sealed reaction vessel, heating to a temperature of about 95° C. to about 115° C. for about 60 hours to about 90 hours to provide 9,10-dihydroxy-2,2,4-trimethyl-1,2-dihydro-5H-chromeno[3,4-f]quinolin-5-one.