The reaction of 10-bromo-5H-dibenzo[a,d]cyclohepten-5-one (I) with N-methylpiperazine (A) by means of potassium tert-butoxide in refluxing tert-butanol gives 10-(N-methylpiperazin-1-yl)-5H-dibenzo[a,d]cyclohepten-5-one (II), which by treatment first with methyllithium in ether and then with refluxing ethanolic HCl is converted into 5-methylene-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-10-one (III). The reaction of (III) with hydroxylamine in refluxing methanol yields 5-methylene-10-hydroxyimino-10,11-dihydro-5H-dibenzo[a,d]cycloheptene (IV), which is reduced with sodium cyanoborohydride in methanol to afford 5-methylene-10-hydroxamino-10,11-dihydro-5H-dibenzo[a,d]cycloheptene (V). The internal reaction of (V) in refluxing xylene gives 5-(hydroxymethyl)-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (V), which is reduced with Zn in hot acetic acid.
Intermediate (III) can be obtained as follows: The reaction of (I) with piperidine (B) by means of potassium tertbutoxide in refluxing tert-butanol gives 10-(1-piperidyl)-5H-dibenzo[a,d]cyclohepten-5-one (XII), which by reaction with methyllithium in ether is converted into 5-hydroxy-5-methyl-10-(1-piperidyl)-5H-dibenzo[a,d]cycloheptene (XIII). Finally, the dehydration of (XIII) in refluxing ethanolic HCl yields (III), already obtained.
The reaction of 5H-dibenzo[a,d]cyclohepten-5-one (VII) with NH3 and TiCl4 in toluene gives 5H-dibenzo[a,d]cycloheptene-5-imine (VIII), which is tosylated with p-toluenesulfonyl chloride in pyridine to yield 5-(p-toluenesulfonimino)-5H-dibenzo[a,d]cycloheptene (IX). The methylation of (IX) with methyllithium in dry THF affords 5-methyl-5-(p-toluenesulfonimido)-5H-dibenzo[a,d]cycloheptene (X), which is internally cyclized by means of KOH in diglyme at 170 C giving 5-methyl-N-(p-toluenesulfonyl)-10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5,10-imine (XI). Finally, this compound is hydrolyzed with aqueous HCl in refluxing AcOH.
A new synthesis of [11C]-labeled MK-801 has been reported: The reaction of 10,11-dihydro-5H-dibenzo[a,d]cycloheptene (I) with N,N-dimethyl-N'-tert-butylformamidine in refluxing toluene gives the formamidine (II), which is alkylated with butyllithium and [11C]-labeled methyl iodide in ether-cyclohexane to yield the 5-methyl derivative (III). Finally, this compound is hydrolyzed with KOH in ethylene glycol.