A straightforward synthetic pathway to phenanthro[9,10-d]heterocycles

A series of new 4,5-o,o-bis(haloaryl)pyrazoles was regioselectively prepare d by a tandem amine exchange/heterocyclization. The intramolecular Stille-t ype biaryl coupling of the so-obtained pyrazole derivatives and previously prepared diarylisox-azoles led with high overall yields to the isolation of new phenanthro [9,10-d]pyrazoles and phenanthro[9,10-d]isoxazoles, respect ively. The formation of dehalogenation products was efficiently avoided by use of heavy-wall pressure tubes.