The present disclosure relates to semiconductor structures and, more particularly, to a soluble self-aligned barrier first for interconnect structure and methods of manufacture. The structure includes: a self-aligning barrier layer lining a trench of an interconnect structure; and an alloy interconnect material over the self-aligned barrier layer. The alloy interconnect material is an alloy composed of metal interconnect material and pre-anneal material that also forms the self-aligning barrier layer.