No, the word előtt needs to come right after az orosz munkások so that you have az orosz munkások előtt somewhere in the sentence. That's the only way you can express "in front of the Russian workers."

The sentence has three parts:

1. The subject a főnök

2. The verb beszél

3. And the phrase az orosz munkások előtt (which tells us where it's happening)

You can arrange those three parts in various orders, but each part has to stay glued together as a unit in order to maintain its meaning.

By starting your sentence with A főnök előtt, you're talking about something happening "in front of the boss," which isn't what you want.

We don't use the accusative because munkások is not the direct object of the verb.

It is part of a prepositional phrase that describes where the action is happening.