Reduce sink drain question

[Randy Edge]

I'm in Florida and have a drain question. I'm finishing out the inside of a detached workshop. In the 'she cave' side, there will be a sink base with a standard kitchen sink. The drain in the slab is 2". The framed walls are 2" x 4". I know at some point it will have to be reduced.
The drain didn't turn up in the right spot for the sink, so I will have to run over through the wall about 4' to get to where the sink will be.
Will I violate any codes by reducing where it stubs through the floor? Or should I get it to the sink and then reduce?
It doesn't really matter to me other than when I hole saw a 2" through the wood there won't be much left on each side of the hole. Thanks.

 

[Terry]

A kitchen sink is 2" waste line, a 1.5" trap and trap arm, and 1.5" vent.
A 1.5" trap can go 42" to the vent.

A hole for 2" pipe is 2-9/16"
A hole for 1.5" pipe can be 2-1/8"

 

[Sponsor]

 

[Randy Edge]

So I need to extend as a 2" over to where it exits the wall for the sink, then reduce to 1.5"? And I need to plan a vent there as well? Would an AAV under the sink work?

 

[Terry]

So I need to extend as a 2" over to where it exits the wall for the sink, then reduce to 1.5"? And I need to plan a vent there as well? Would an AAV under the sink work?

An AAV under the sink works as a vent since you have an vent through the roof other places.
At least 4" above the trap arm.