I can not drawing pipe rectang to circle, help me, please!
And you better to divide the circle in the same number of edge of the pentangon to let the LOFT to match the vertex easier.
That’s why I rebuilt the circle to degree 3 with 5 spans ; )
Developable surface which can be unrolled flat without stretching.
Divide the circle into 5 segments.
Loft between a point at each vertex of the pentagon and a circle segment.
Loft between a point at the end of each circle segment and a pentagon side.
Join if needed.
This is a common method to build such shapes in sheet metal for ducts and similar. It can be made by simple folding and rolling without any stretching. The shapes shown above are smoother but require stretching to build from sheet metal.
If only forum users wouldn’t keep their needs and requirements top secret 
as long as we helping forum people are bored enough to bite into any stupid (could not be bothered to learn less than the basics) bone it will work.