Coupled vs Decoupled backend-frontend

I have an asp.net website project that uses APIs as a back-end, i need to totally decouple my front-end from my back-end apis, so I have created one RESTful service in my back-end project and now i want to consume it in the front-end. I assume i have two solutions:

• Build my model only in the back-end, and add reference to the front-end, it will help avoid re-writing the same model in the front-end again.
• Build two models in both back-end and front-end.

Pros: Solution 1) - it will help avoid re-writing the same model in the front-end again. - it will force front-end to be updated once the back-end changes.

Solution 2) - It should help decoupling my front-end from the back-end. - It won't function if my back-end changes, but it will avoid build errors.

Please advise which approach is better design, and if you have suggestions please share.