Title: Is Intercourse Allowed If Ghusl Can't Be Performed Before Prayer?
English:
Question #189:
One knows that if he becomes junub by having intercourse with his wife, he would have no water for the ghusl or there would not be enough time for both ghusl and prayers, is it permissible for him to have intercourse?
Answer #189:
Although it is not possible for him to make ghusl, there is no objection to having intercourse with his wife if he is able to perform tayammum.
-Imam Khamenei, Practical Laws of Islam, Rules of Ghusl Janābah