The condensation of diethyl (2-methoxyphenoxy)malonate (I) with pyrimidine-2-carboxamidine (II) by means of NaOMe (Na in MeOH), followed by treatment with NaOH, provides the dihydroxy pyrimidine derivative (III), which is converted into the dichloro derivative (IV) by treatment with refluxing PCl5 and DIEA. Compound (IV) can also be obtained from the pyrimidinedione (V) by reaction with phosphorus oxychloride at 90 C. Reaction of compound (IV) with 4-tert-butylbenzenesulfonamide (VI), performed either directly in DMSO or by means of benzyltriethylammonium chloride (BTEAC) or tetrabutylammonium bromide (TBAB) and K2CO3 in refluxing toluene, gives compound (VII). Finally, this compound is converted into bosentan by reaction with sodium and ethylene glycol (VIII). Alternatively, the conversion of compound (VII) into bosentan can also be performed by reaction of compound (VII) with ethylene glycol mono tert-butyl ether (IX) by means of NaOH in toluene, yielding the tert-butyl ether derivative (X), which is then treated with formic acid at 85-90 C in toluene to give the 2-(formyloxy)ethoxy derivative (XI). Finally, the formyl group is removed by treatment of (XI) with NaOH in H2O.

The condensation of diethyl (2-methoxyphenoxy)malonate (I) with pyrimidine-2-carboxamidine (II) by means of NaOMe (Na in MeOH), followed by treatment with NaOH, provides the dihydroxy pyrimidine derivative (III), which is converted into the dichloro derivative (IV) by treatment with refluxing PCl5 and DIEA. Compound (IV) can also be obtained from the pyrimidinedione (V) by reaction with phosphorus oxychloride at 90 C. Reaction of compound (IV) with 4-tert-butylbenzenesulfonamide (VI), performed either directly in DMSO or by means of benzyltriethylammonium chloride (BTEAC) or tetrabutylammonium bromide (TBAB) and K2CO3 in refluxing toluene, gives compound (VII). Finally, this compound is converted into bosentan by reaction with sodium and ethylene glycol (VIII). Alternatively, the conversion of compound (VII) into bosentan can also be performed by reaction of compound (VII) with ethylene glycol mono tert-butyl ether (IX) by means of NaOH in toluene, yielding the tert-butyl ether derivative (X), which is then treated with formic acid at 85-90 C in toluene to give the 2-(formyloxy)ethoxy derivative (XI). Finally, the formyl group is removed by treatment of (XI) with NaOH in H2O.

The condensation of diethyl (2-methoxyphenoxy)malonate (I) with pyrimidine-2-carboxamidine (II) by means of NaOMe (Na in MeOH), followed by treatment with NaOH, provides the dihydroxy pyrimidine derivative (III), which is converted into the dichloro derivative (IV) by treatment with refluxing PCl5 and DIEA. Compound (IV) can also be obtained from the pyrimidinedione (V) by reaction with phosphorus oxychloride at 90 C. Reaction of compound (IV) with 4-tert-butylbenzenesulfonamide (VI), performed either directly in DMSO or by means of benzyltriethylammonium chloride (BTEAC) or tetrabutylammonium bromide (TBAB) and K2CO3 in refluxing toluene, gives compound (VII). Finally, this compound is converted into bosentan by reaction with sodium and ethylene glycol (VIII). Alternatively, the conversion of compound (VII) into bosentan can also be performed by reaction of compound (VII) with ethylene glycol mono tert-butyl ether (IX) by means of NaOH in toluene, yielding the tert-butyl ether derivative (X), which is then treated with formic acid at 85-90 C in toluene to give the 2-(formyloxy)ethoxy derivative (XI). Finally, the formyl group is removed by treatment of (XI) with NaOH in H2O.

The condensation of diethyl (2-methoxyphenoxy)malonate (I) with pyrimidine-2-carboxamidine (II) by means of NaOMe (Na in MeOH), followed by treatment with NaOH, provides the dihydroxy pyrimidine derivative (III), which is converted into the dichloro derivative (IV) by treatment with refluxing PCl5 and DIEA. Compound (IV) can also be obtained from the pyrimidinedione (V) by reaction with phosphorus oxychloride at 90 C. Reaction of compound (IV) with 4-tert-butylbenzenesulfonamide (VI), performed either directly in DMSO or by means of benzyltriethylammonium chloride (BTEAC) or tetrabutylammonium bromide (TBAB) and K2CO3 in refluxing toluene, gives compound (VII). Finally, this compound is converted into bosentan by reaction with sodium and ethylene glycol (VIII). Alternatively, the conversion of compound (VII) into bosentan can also be performed by reaction of compound (VII) with ethylene glycol mono tert-butyl ether (IX) by means of NaOH in toluene, yielding the tert-butyl ether derivative (X), which is then treated with formic acid at 85-90 C in toluene to give the 2-(formyloxy)ethoxy derivative (XI). Finally, the formyl group is removed by treatment of (XI) with NaOH in H2O.

The conversion of 2-chloropyrimidine (I) to pyrimidine-2-carboxamidine (III) is performed by known methods through the intermediate pyrimidine-2-carbonitrile (II). The cyclization of (III) with 2-(2-methoxyphenoxy)malonic acid diethyl ester (IV) -prepared by condensation of 2-chloromalonic acid diethyl ester (V) with guaiacol (VI)- yields the bipyrimidinedione (VII). This compound is treated with refluxing POCl3 to afford the dichlorobipyrimidine (VIII). The chlorine monosubstitution in (VIII) with 4-tert-butylphenylsulfonamide (IX), K2CO3 and tetrabutylammonium bromide (TBAB) in toluene provides the substituted sulfonamide (X), which is submitted to a second chlorine substitution with ethyleneglycol mono-tert-butyl ether (XI) by means of NaOH in hot toluene to give the tert-butyl-intermediate (XII). Finally, this compound is deprotected by reaction with formic acid yielding the formate ester (XIII), which is hydrolyzed with NaOH in ethanol/water, and submitted to crystallization in refluxing ethanol/water to afford the target bosentan.