I joined a professor and soon found that his style and mine were not compatible at all. His style is as follows: dictatorial, gives you a problem statement and gives some hints to solve it, extremely presentation oriented and does not listen to you when you give updates on work, gives only inputs on style of presentation etc 99% of the time. I didn't make any technical progress for a year and a half. Finally I got a co-guide from another university with whom I got along really well and completed a project within 4 months. Now my main professor also dictates the co-guides to guide in his style only. Since I am not able to work in his style, I have again slowed down drastically for the last 6 months or so. I had completed a piece of work I completed and he has not reviewed it since last november despite repeated emails and reminders. He also takes offense if you submit it without his permission and considers it a sign of insubordination. I also tried to solve the communication problem with my main professor by asking my lab mates. But they really don't help me. Another problem is that I am already 36 years old and a majority of my lab mates are in their 20's. Also, I am basically a very shy person who is not good at interacting with people. There are people in my lab who don't have publications even though they are in their 5th year of phd. People who have completed have taken around 7 to 8 years. My co-guide was initially very helpful and understanding. I am really depressed and not able to focus on anything. But could you please suggest what I can do to rectify things here if possible. My guide and co-guide are good friends and I am not confident of them helping me. I am thinking of applying for a new phd position, but am really confused and lost.

It sounds like you are well into your second year.
If you have a clear idea of what you are doing I would be considering breaking away from your supervisor and working independently. This is my advice for working with all poisonous or incompatible people. If independent working doesn't solve it, I would be considering other options such as finding other opportunities.

Are you in the UK? I ask because if you are, 7 to 8 years is ridiculous.
Your age should not be a concern. I did my PhD in my mid to late 40s. Many people do this in their later years,

In summary, you have to look for areas to take control of your PhD.

That is true. I am almost in my 3rd year. I am not in the UK. I had also considered working independently but he does not permit it. It is like he does not tell you what he wants. He expects us to guess what he wants and do it. If not, the same task goes on for months and you will have nothing. I usually can think of multiple ways of doing a task. I analyze by myself and perform it in a way which seems to be the best at the moment. He also doesn't permit his students to go for external internships or anything. What scares me is that he is extremely powerful and well-known in my field and this situation really gives me panic attacks.

I understand how bad this can make you feel and how much it impacts on your work. I also had compatibility issues with my supervisor. I also started working with another researcher with whom I was more compatible. I then went on to postdoc with that person. No matter what anyone says, having a degree of compatibility with your supervisor is vital. By the sounds of it, you and this supervisor are just not compatible.

I agree with pm133's advice about maybe just trying to be more independent as a solution to this. But, just to share in case it's helpful, I also tried this with my supervisor, and it was nightmarish. Basically, in the same way that YOU have a way of working and being productive, the supervisor also has a way of supervising. So he may not like you taking your own path and it may turn out being a real headache. For example, he could refuse to give you any feedback at all, or you could get a bad reputation for being a "trouble" student. And more importantly, at the end of the day, the PhD is supposed to be an apprenticeship in research...you are not yet a fully independent researcher... you are supposed to be being mentored as you complete your research. So going solo at this stage (which is pretty much what I did half way through my PhD) isn't ideal if it can be avoided.

Ideally, I think you'd want to switch supervisors to the one you work well with... But with them being friends, you would need to tread very carefully, as there is always politics at play and you don't want to blow it with both of them. One solution might be to come up with some reason why you need to have the co-guide as your main supervisor... could you change the focus of your project to be more in line with their specialism, so that you end up getting your main input from the other one, either formally or informally?

Are you in a position to do this? Could you go to a different lab and start a new PhD? And could you be sure you would get on well with the supervisor? If that REALLY is an option, then I would certainly be considering it. The lab doesn't sound great if it is taking people that long to complete and they aren't publishing...

Another suggestion... could you continue collaborating on separate projects with the co - guide and build up your publication record that way, meanwhile going through the motions with your PhD? That way you would have some papers and it could lead to a postdoc with them? No one really cares about how good the thesis was or wasn't once you've got the PhD, so you could treat it more like a (rather big) box ticking exercise and have your real passion and focus on the other work you are doing...

Being well known in his field isn't really relevant because as you've said, the group doesn't appear to be very good at publishing.
In what way is he powerful?

He is the dean of my institution. He also chairs several important conferences in my field. He is involved in many activities and doesn't have time for students.

In which case I would tell him that I needed more supervision than he is able to provide and would ask if he would support another supervisor taking that task on.
How you phrase these things needs great care to ensure it doesn't sound critical or aggressive but him being very busy is the leverage you need to make the change.

I'm all for upfrontness, but think it's better to say it is about your changing research interests... Less room for it to be taken personally / as a criticism of supervisory style/input.

TQ, if changing research interests is genuinely the case then that probably is a better approach. The problem is that if you pretend the problem is one thing when it isn't, you risk having your bluff called. Whatever approach is taken, my advice would be that it is grounded in reality. If you are caught lying about the reason for wanting to move supervisor, he might see straight through it and that might cause more problems than it solves.

It's a difficult situation without a doubt.

I don't mean lie. I mean emphasize something else. Emphasize the cosupervisor's area of science - even that mini project he did with that supervisor - and how it chimes with his interests, he wants to go more in that direction. Then it's about the science. Much easier.

A friend of mine switched her PhD and this was her overt reason for doing so. The real driving factor was that she did not get on with the style of one of her supervisors. It worked, she had no regrets, and there was no need for confrontation or controversy.

Anyway I wonder if one of our suggestions could work...