You can find portal.properties in portal-impl.jar

Create a classes folder under your ROOT.war/WEB-INF. Place your portal-ext.properties file there and check the portal.properties file in portal-impl.jar as a reference for properties you would like to override in portal-ext.properties.

For more information, check this post: http://www.liferay.com/web/guest/community/forums/-/message_boards/message/552844

You can also override the values straight from portal.properties......

Were you able to override those values that you needed? If not, could you provide a bit more information on what have you done

PS. You don't need to extract jar file in order to be able to override values from portal.properties

So you have tried placing folder classes under WEB-INF and file portal-ext.properties under that and it fails, interesting......

Could you provide a bit more information related to error message, etc. from console?

BR - Lari