Those from which you want to copy metadata - "the source files"
Those to which you want to paste metadata - "the target files"
Use the menu item Library > Sync files with same name or time
For "Copy metadata from files of this type", the first drop-down box, select the file type which has the metadata that you want to copy.
In the second drop-down box "to matching files of this type", choose the file type whose metadata you want to update.
"Match using" defaults to the file name, but choose Capture time if that is appropriate
By default, Syncomatic updates all IPTC and IPTC Extension fields. If you want, you can untick Ratings, Labels, Title, Caption and Keywords.
Syncomatic can update Develop adjustments - just tick the box.
Check Keywords if you wish
Merge Keywords means that Syncomatic will add keywords from the source files to the keywords already applied to the target files. If this is unchecked, any existing keywords in the target files will be removed.
Click OK and you'll see the ratings and other metadata will be synchronised:
Note that Syncomatic crop and rotation updates may be unreliable because Adobe have no published method of updating these settings by plugin.
Notice how the JPEGs now have ratings which match the raw files.