Faced this problem when trying to build android using ionic2/cordova. Seems like com.android.tools.build:gradle:2.2.3 is not listed in maven.org (but is available in jcenter).
I was able to compile and run it using Android studio 2. Would still trying to find a better solution here.
After some time, this error comes from CordovaLib (reference projects for Cordova). To resolve this, I edit "build.gradle", remove mavenCentral to make it look like code below :-
Next, i was able issue 'cordova compile" or "ionic build android" to build my project successfully. (You can't use ionic command as it would replace the entire project file).
Problem solved! :) Unless, you completed remove Android source in platform folder.
Update : This is fixed in Ionic Framework release 2.0.0