iphone 4s doesn't sync with iTunes

You need to install the new iTunes on the computer, not on the phone. Install and try to sync again.

Hi. Apple Mobile Device Support is the key unit for recognizing your iPhone by iTunes. Try to update your iTunes to latest version on your PC or Mac. If it does't work, try to remove iTunes and reinstall it:

iPhone, iPad, or iPod not recognized in iTunes for Windows - Apple Support

If you don't see your connected device in iTunes for Mac - Apple Support

Remove and reinstall iTunes and related software components for Windows Vista, Windows 7, or Windows 8 - Apple Support

Regards,

Anson