Not able to transfer purchases from iPhone (iOS 9.1) to iTunes (Mac Book)

What happens when you try to transfer them, and you are using the File > Devices > Transfer Purchases menu option ?

You may also be able to redownload them directly on your Mac's iTunes via the Purchased link under Quick Links on the right-hand side of the iTunes store homepage

What type of purchases are they ? If they are apps then with iOS 9 they I don't think that will copy back, possibly due to a new developer feature that is/will be available :

The store and operating system optimize the installation of iOS, tvOS, and watchOS apps by tailoring app delivery to the capabilities of the user’s particular device, with minimal footprint. This optimization, called app thinning, lets you create apps that use the most device features, occupy minimum disk space, and accommodate future updates that can be applied by Apple. Faster downloads and more space for other apps and content provides a better user experience.

So only what is needed by an app on a device will be downloaded onto the device, it might not be the complete app.