That is really, really difficult for you.
The thing about ASD is that it requires intervention from an early age, so it's really hard to undo or work with things like the constant interrupting. My DS is autistic and I worked in a school until very recently for autistic children. My DH is also Asperger's. I'm surrounded! ASDers don't do well with dialogue. It's their biggest challenge. DH can go on talking for ages and ages. I dread bringing him to social occasions because he will take the mike and not step off the podium; even as people's attention spans drop like flies, he'll rabbit on and on. My DS has this issue (but he's 5 and I can use strategies to work with this). DH interrupts me all the time. Drives me mental.
So the thing I notice is that they're voice/opinion is the dominant one and on top of that, their opinion is the right one. And it is mighty hard to make headway when they hold such firm ground.
So what you don't need to do is worry about being polite. Just be straight. He will respond very well to direct, straight, honest talk. No airs and graces. People on the spectrum tend to do very well with the truth. You'll sort of have to tell him "I need to speak now." You'll need to stop him from talking and guide him into listening to you with brute force: "I am going to speak now."
Believe me, he'll return to what he wanted to say once you're done. So, don't worry about interrupting him.
Probably discussion in large groups/round table discussions is something to keep at a minimum with your boss. One-to-one works much better.
Speak in facts and information. Emotions, which, ironically can run incredibly deeply for a person on the spectrum, tend not to come into the world of speech. They tend to speak about and respond to clear, factual information. You may have to point out to your boss that, "John might be upset if you decide to go with plan A because plan A puts John at risk of losing his job and income, which will worry his family and cause stress in the household."
Cause and effect.
Everything has a consequence. So with a person on the spectrum, you have to be like, "We are doing it this way because this will happen when we do it this way."
You don't say, "Don't eat those berries."
You don't even say, "Don't eat those berries because those ones are poisonous."
What you say is, "Don't eat those berries because those ones are poisonous and they will make you ill (and you really don't want to be ill)."
Just keep thinking, he thinks in 'cause and effect' terms.
If we do this, this happens. If we don't do this, that happens.
When you open up a thought and share it with him, you have to close that thought and complete it.
God, does any of this make sense?
Often you need to be a human stop sign.
You have to stop them and say, "I am going to talk now," or "We are now finished. Let's move onto our next discussion."
Do it nicely and gently. It's the words you use that matter.
Hope this helps, somewhat.