No idea if this could be done with some clever copy&paste mechanism,
but you can copy the whole document and use the following macro to zap
the non-outline part of it.

Public Sub KillBodyText()
    Dim para As Paragraph
    For Each para In ActiveDocument.Paragraphs
        If para.OutlineLevel = wdOutlineLevelBodyText Then
            para.Range.Delete
        End If
    Next
End Sub

HTH, Markus

One way to do this is to create a TOC based on the content (easy to do if
you have used outline levels or heading styles); see
http://www.ShaunaKelly.com/word/toc/CreateATOC.html for the basics. Create
the TOC based on the outline levels you want to include. Copy it and paste
it into a new document, then immediately Ctrl+Shift+F9 to unlink the field
and convert the TOC field to plain text. You can then delete the TOC from
the original document if desired.