Mercuric acetate cyclization of -(arylmethyl)piperidines; synthesis of indolo [,-g]morphans (tetracyclic ring system of strychnos indole alkaloids) and ,-benzomorphans
3-g]morphans and 7,8-benzomorphans is reported. The key step in these syntheses is the mercuric acetate oxidation of appropriate 2-(4-piperidylmethyl) indoles or 4-benzylpiperidines, respectively. An alternative synthetic entry to 2-(4-piperidylmethyl)indoles, consisting in Wadsworth-Emmons condensation of a suitable 4-piperidone with diethyl 2-oxopropylphosphonate followed by catalytic hydrogenation and
The regloselectivity of the Fischerindolesynthesisfrom 2-azabicyclo[3.3.1]nonan-7-ones 4b–d using three different acid catalysts is studied, an ethyl substituent at the 9-position promoting indolization upon the C-8 carbon.