[C#] Unity asks for a } for a reason I don't know ( '}' expected )

I’ve tried a bunch of fixes to this but none have worked, I feel that this is a rather simple fix. Any help?

using UnityEngine;
using System.Collections;
using UnityEngine.SceneManagement;

public class toMainMenu : MonoBehaviour {

	void Update( )
		if( Input.GetKeyUp( KeyCode.Escape ) ){
			SceneManager.LoadScene(string MainMenu1);

Brackets come in pairs - an open and a close. Right now, your code has 3 opening curly brackets, and only one closing curly bracket. So put two more } at the end.