From the time of amud hashachar, it is prohibited to deal with one’s work before praying. This is because holy matters precede secular matters and the respect of Heaven precedes the needs of people. Therefore, it is necessary to first thank Hashem in prayer, and only afterwards deal with one’s own needs. The Chachamim teach (Berachot 14a), “Anyone who prays and afterwards goes on his way, HaKadosh Baruch Hu grants him what he desires.”
It is preferable to pray individually before beginning to work, instead of praying in a minyan after he has begun to work. For example, if a person must start work at 6:30 a.m. and the only minyan in the area is at 7:30 a.m., it is better that he prays individually before work begins, so that he does not work prior to praying (Mishnah Berurah 89:20).
However, before amud hashachar, a person is permitted to deal with his work, for since the time of Shacharit has not yet arrived, he is not considered to be putting his needs before prayer. He must be strict in saying Birkot HaShachar before that, for the time to recite them is immediately upon waking up. Since he started his work before the time to pray began, he is permitted to continue even after amud hashachar on condition that he succeeds in praying before the time to pray lapses (Shulchan Aruch 89:7; Mishnah Berurah 89:37; 70:23).