I remember asking this question once. The professional I consulted is very rigorous with his work (he was a book editor at Springer). He replied that, in general, high quality paper should be read from top to bottom without looking up, and be as accurate and austere as possible. His answer at first seemed rather vague to me, but believe me, that's practically what it's all about: communicating as well as possible.
As an early interpretation, if you need to give a theorem at the beginning and then prove it at the end, you must take care that the reader does not have to read the theorem again. The only thing that changes is the elegance with which you achieve it.
For example, if your paper deals with a problem you solve, it is better:
- Initiate a brief introduction to the problem (taking the opportunity
to introduce references).
- Formulate the theorem as a problem,
conjecture, or something unresolved: state things as you found them. Remember, it's not a good idea to rush through everything at first; the trick is to induce the reader to want to read your work to the end more than anything else in the world.
- If your development is very long, you can also add an "outline" of how you have structured your paper to reach the solution, so the reader will not get lost in the tangle of reasoning.
- In each development, explain in human words what you are going to do or the results you get; you can take advantage of this to show how you advance in the "outline" of the paper you gave before.
In this way the reader will be imbued with the problem and will keep it in mind. Then, after all the propositions, lemmas, etc., enunciate the final theorem with its proof.
Your question is ultimately about how you structure the paper for the best possible communication; whether or not to use a theorem or problem or both to enunciate and develop its content is pure strategy. For the structuring of the paper, there are several interesting books. One that served me well is Writing Science.
To see more specific strategies, I strongly recommend that you decide beforehand which journal you will publish in, and review how the other authors have structured their work. Look at a lot of them, so you get the average idea. It is also very good to review high-impact journals; although it is difficult for you to understand their content, focus on understanding the structure of the explanation, which is more important (of course, you can take advantage of this to read your references in detail).
If you still want to keep your theorem at the beginning and your proof at the end, and if you write in LaTeX then you can call the
proof environment with the optional parameter
[Proof of Theorem <enumeration-here>].