Email on Saturday for sponsoring conference participation on Sunday

I just came across a conference + short course that might be very relevant and interesting for my company. Unfortunately, this conference starts in one day and today is Saturday.

So, to get the approval and the green light for funding from management (for conference, accommodation/travel, plus attending during work time), I'd have to send a last minute email today, during the weekend, and have someone spend time to approve or deny my request.

Is this considered inappropriate? Or it is seen positively if the conference does interest the company?

This depends a lot on company culture and the people involved, but there goes

Is this considered inappropriate?

Yes, at least in my opinion. First of all reaching out to colleagues during the weekend for non-emergency reasons is sort of disrespectful. It shows that you feel your work related issues are more important than other people's free time. It is also a sign of poor planning. If that conference is so relevant and so interesting, how come nobody knew about it earlier than last minute?

This a non-trivial request for significant funds and time-off on extremely short notice. Most companies have approval processes for these that will need to be followed and this needs to be done during work hours (unless its a dire emergency).

In most companies that would be a no-go.

Maybe if the company is very small with little or no formal policies and the CTO is a big fan of these type of conferences/activities you can ask, but even then it's unlikely to be approved.