[SVXX]

One of my friends gave me this puzzling question two days earlier and I haven't been able to figure it out. I have a substrate pentan-2,4-dione, and I have to perform a Clemmensen reduction on it. My first answer was that both ketone groups would be reduced but my friend said that the answer is more complicated than that.
The final product is 3-methylbutan-2-one. A little surprising, as this suggests there has been a rearrangement(and hence loss of one carbon in the main chain). Any mechanism suggestions for this, forumers?
PS : I think there would be a carbon-radical, oxygen-anion mechanism for this, but I don't really know.

[AWK]

http://pubs.acs.org/doi/pdf/10.1021/jo01017a512

[SVXX]

Wow...exactly what I needed..so it's a pinacol-type rearrangement which occurs in acidic medium. Thanks a lot AWK!