The concept of a central dogma is largely taboo, but you do get pretty good milage in calling the priority of Union in our Union with Christ the central dogma of the Reformed branch of the reformation.
Union is largely a practical implementation of Christological Pneumatology, so you can find resources regarding the underlying concepts over in the Pneumatology section.
Union with Christ: An Introduction (Jeff Waddington)
Justified in Christ: God's Plan for us in Justification (Scott Oliphint, ed.)
Chapter 2: Union with Christ and Justification (Lane Tipton)
Life in Christ: Union with Christ and Twofold Grace in Calvin's Theology (Mark Garcia)
Somewhat advanced; Deep work exhaustively covering various facets of Calvin's doctrine.
Resurrection and Redemption: A Study in Paul's Soteriology (Richard Gaffin)
You might think of this as Union "internals"; Union is all about the resurrection.
Redemption Accomplished and Applied (John Murray)
Though not perfect, it's generally considered required reading.
The Triune Gift of Self a Reformed Critique of Karl Rahner's Theology of Divine Self-communication (Camden Bucey)
Chapter 8.2ff. Excellent explanation of glorification as it related to Union with Christ.
The Holy Spirit (Sinclair Ferguson)
I'd love to provide a specific chapter, but Union isn't an isolated topic.
John Flavel On The Priority Of Union With Christ: Further Historical Perspective On The Structure Of Reformed Soteriology (William Edwards)
The Inexhaustible Fountain of All Good Things: Union with Christ in Calvin on Ephesians (Lee Gatiss)
People tend to debate Union in Calvin from the Institutes. Dr. Gatiss goes to the Ephesians sermons to additional clarity.
Biblical Theology and the Westminster Standards (Richard Gaffin)
Good examination of the Standards with good treatment of Calvin's Institutes.
Biblical Theology and the Westminster Standards Revisited: Union with Christ and Justification "Sola Fide" (Lane Tipton)
Good examination of the Standards with references to John Murray's work; also, an examination of Louis Berkhof's work.
Footnote in Redemptive History and Biblical Interpretation (Geerhardus Vos)
Mark Garcia's Corrections of John Fesko (Mark Garcia)
Fesko makes quite a number of factual mistakes in his own work that needed to be addressed.
The Place of the Resurrection in Pauline Soteriology (Richard Gaffin)
3 part series focusing on the life that Christ provides; strong focus on sanctification.
Resurrection in the Theology of Paul (Richard Gaffin)
In the Reformed Unionist tradition, Resurrection and Union are relates closer than in other traditions. In this RTS series, Richard Gaffin dives into the Resurrection, thus into Union, similar to how he did in Resurrection and Redemption.
Life Giving Spirit: The Exaltation of Christ and Salvation in the Theology of Paul (Richard Gaffin)
The work of the Spirit is the work of Christ, thus, this work on the Holy Spirit dives deeper into Who this Christ is and how we receive the benefits by Union.
- Union with Christ and Twofold Grace (Mark Garcia)
- The Justification Landscape (Mark Garcia)
- Lane Tipton's Discussion
- Michael Horton's Response
- Michael Horton and Lane Tipton Dialog
- (counseling application at end) Biblical Psychology and the New Perspective on Paul (Paul Maxwell)
- John Flavel and Union
- Bibliography (starts about half way through)