The reduction of 3,5-dimethoxybenzoic acid (I) first with Li in liquid NH3 and methanol, and then with LiAlH4 in THF gives 3,5-dimethoxy-1,4-dihydrobenzyl alcohol (II), which is cyclized with phenylhydrazine (III) in refluxing 4% sulfuric acid yielding 2-(hydroxymethyl)-1,2,3,4-tetrahydrocarbazol-4-one (IV). The reaction of (IV) with tosyl chloride in pyridine affords the corresponding tosylate (V), which is finally condensed with 4-(4-fluorobenzoyl)piperidine (VI) in N-methyl-2-pyrrolidone.
The reduction of 3,5-dimethoxybenzoic acid (I) first with Li in liquid NH3 and methanol, and then with LiAlH4 in THF gives 3,5-dimethoxy-1,4-dihydrobenzyl alcohol (II), which is cyclized with phenylhydrazine (III) in refluxing 4% sulfuric acid yielding 2-(hydroxymethyl)-1,2,3,4-tetrahydrocarbazol-4-one (IV). The reaction of (IV) with tosyl chloride in pyridine affords the corresponding tosylate (V), which is finally condensed with 4-(6-fluoro-1,2-benzisoxazol-3-yl)piperidine (VI) in N-methyl-2-pyrrolidone.
The condensation of 3,5-dimethoxybenzoic acid (I) with 4-(4-fluorobenzoyl)piperidine (II) by means of DCC and HOBT in DMF gives the piperidide (III), which is reduced with LiAlH4 in THF to yield 1-(3,5-dimethoxybenzyl)-4-(4-fluorobenzoyl)piperidine (IV). The reduction of (IV) with Li in liquid ammonia affords the 1,4-dihydro derivative (V), which is finally cyclized with phenylhydrazine (VI) in refluxing aqueous sulfuric acid to provide the target tetrahydrocarbazolone.
The condensation of 3,5-dimethoxybenzoic acid (I) with 4-(6-fluoro-1,2-benzisoxazol-3-yl)piperidine (II) by means of DCC and HOBT in DMF gives the piperidide (III), which is reduced with LiAlH4 in THF to yield 1-(3,5-dimethoxybenzyl)-4-(6-fluoro-1,2-benzisoxazol-3-yl)piperidine (IV). The reduction of (IV) with Li in liquid ammonia affords the 1,4-dihydro derivative (V), which is finally cyclized with phenylhydrazine (VI) in refluxing aqueous sulfuric acid to provide the target tetrahydrocarbazolone.