Can someone give me a run down of D-D reactions and H-B reactions?

I know that
He3 + He3 -> He4 + 2p
D + T -> He4 + n
D + Li6 -> 2He4
4H -> He4 + 2e+

Presumably D-D goes
D + D -> He4
but where do the neutrons come from? Are they a catalyst like D-Li6?