An easy to solve problem.
Now it's possible to convert a C4D material to Arnold Standard Shader with scripts placed in utility -> Materials -> ....
But a ver big problem is how reverse this operation, I mean from Standard Shader to C4D Shaders.... Why? When yo export an scene in FBX with Arnold Shaders Materials applied seems that any assignation will be preserved. But with C4D standard materials all assignations become stored in FBX file.
This is a big problem if you have hundred of Arnold shaders materials assigned and you need pass those assignation throught FBX files. I have not found a method to convert an Arnold Shader to C4D material, It's not necesary preserve Arnold Shader appareancy (altought a random color by each C4D material restored would be great) in this case with a solid it's ok if like me you only need preserve material assignations.
It would be nice a script in utility -> Materials -> "Restore selection to C4D material"