Alternative syntheses of spacer linked hetero biaryls: Examples

Due to the above mentioned low yields of the halogen dance reaction leading to (2a) in combination with the need of substrates for the planned ring-opening reactions a different synthetic approach had to be developed. This was even much more important as (2a) was not only a target itself but also the key-intermediate for another compound to be aimed at, i.e. di-thienylethylene (2b).



Scheme 11

The benzene spacer compound (2c) could also to be synthesized by an alternative utilizing Pd(0) coupling chemistry.



Scheme 12