[ALUG] Problem with 'find' and 'basename'

I'm trying to change the suffix of all files in a directory hierarchy.

Trying to diagnose my problem I have run the following command:-

find info -name '*.txt' -exec echo `basename {} .txt` ;

A section of the output from the above command is as follows:-

info/motorbikes/zzr1200service.txt info/motorbikes/luggage.txt info/motorbikes/index.txt info/motorbikes/restindex.txt info/motorbikes/zzr1200info.txt info/motorbikes/lifts.txt info/index.txt info/test/test1.txt info/test/test2.txt info/test/test3.txt

So the `basename {} .txt` is doing nothing at all, why?

Looking further it seems as if the `` inside the find are causing the problem as:-

find info -name '*.txt' -exec basename {} .txt ;

produces the expected output:-

zzr1200service luggage index restindex zzr1200info lifts index test1 test2 test3

The actual command I want to execute is:-

find info -name '*.txt' -exec mv `basename {} .txt`.rst ;

to change the .txt suffix to .rst.

Any ideas how to do it?