No. The X99 is socket 2011-3 and the 7700k is 1151. In terms of overall performance it would also be a bit of downgrade. The 6800k has 2 more cores and 4 more threads and the IPC is not far off so in multi threaded tasks the 6800 is better. In gaming and low threaded programs the 7700k is a bit faster but not by alot.
Have you tried overclocking the 6800k to get a bit more speed?