Have you tried this more than once?  Make sure you are fully inserting plug in the mic jack.  

There is no logic to this.  If it works in rear mic jack and another mic works OK in the front mic jack then this should also work.

Can confirm the same for me using Bose QC15. Cannot figure it out.

So, if the front mic. jack doesn't work with any mic., then the wiring from the MB to the front mic. jack is broken.

what do you mean an audio splitter?   the bose come with a mic that plugs into the headphones

The Alienware Aurora (just the plain Aurora, I didn't look at the specs for the ALX or R models) has separate headphone and mic jacks.  If you have a combo headphone/mic unit with one plug it (e.g. a "TRRS" plug like is used in some gaming consoles and smart phones) it will not work.  If you have this type, an adapter cable is needed to split the headphone and mic into separate "TRS" plugs.  

But, if the rear works and front does not with the separate mic and headphone plugs, it could be the interconnecting cable between the I/O panel and the motherboard.  May be the cable just needs reseating (unplugging and plugging back in).  Or it could be a hardware problem with the I/O panel. 

Many possibilities, that have to be sorted out as to which is the problem.  

You can convert TRRS back to the Red and Green via an adapter cable.

This is what I use for my RECON headset.

https://www.turtlebeach.com/products/recon-50x-headset

https://www.amazon.com/MillSO-3-5mm-Jack-Adapter-CTIA/dp/B071NDLCGC