Final answer:
In a Robinson annulation, the two neutral organic starting materials typically used are a ketone with an α-hydrogen and a methyl vinyl ketone.
Step-by-step explanation:
The Robinson annulation is an organic reaction used to construct cyclic structures by forming a new ring onto a ketone via a Michael addition followed by an aldol condensation. For a synthesize a compound through a Robinson annulation, the two neutral organic starting materials you would typically need are a ketone with at least one α-hydrogen (which acts as the Michael donor) and a methyl vinyl ketone (which acts as the Michael acceptor). As an example, for the synthesis of a compound like 2,5-dimethyl-3,4-diphenylcyclopentadienone, you would use 2,5-dimethylcyclopentadienone and methyl vinyl ketone as your starting materials.