find -execdir + sed problem

[Micha Feigin <michf@post.tau.ac.il>]

I'm trying to fix the file suffix on some file in my directories using sed and
find but for some reason sed doesn't match the string in this manner, that is
running
find . -name "*.JPG.jpg" -execdir echo `echo '{}' | sed -e 's/\(.*\).JPG.jpg/\1.jpg/' -` \;
on a directory with
2005_10_09-03_05_11.JPG.jpg
prints
2005_10_09-03_05_11.JPG.jpg
instead of
2005_10_09-03_05_11.jpg

any idea what I'm doing wrong?

find . -type f -exec echo `echo '{}' | tr "[:upper:]" "[:lower:]"` \;

also fails to convert the file to lower case for some reason (same problem,
doesn't change the case, as if it doesn't see the characters).

Thanks