Draw a reaction using broadly defined R-groups, then search.

Use Query builder.

In addition to locking atoms, chains, or rings, you can specify:
Specify bonds to form or break with 
Map atoms with 
Right-click a bond and select Bond properties. Under Reacting center, click an appropriate option.
To map atoms, click
, click an atom in the reactant, and then drag your cursor over to the appropriate atom in the product.
Or:

"Text" refers to titles, abstracts, and descriptive terms in database records.
Click Create Retrosynthesis Plan within a substance record.
Use
in a substance record to generate potential synthetic pathways