When there are no elders in a congregation and the church chooses certain men to lead, is this scriptural?
I probably would need more information to answer your question. Much depends on what you mean by "lead." During worship service there are men who lead various parts of the worship. "How is it then, brethren? Whenever you come together, each of you has a psalm, has a teaching, has a tongue, has a revelation, has an interpretation. Let all things be done for edification" (I Corinthians 14:26). For instance, we call the man who leads singing at a worship service the song leader.
A preacher also holds authority. "Speak these things, exhort, and rebuke with all authority. Let no one despise you" (Titus 2:15). The nature of his duties naturally causes him to be a leader in a congregation, yet congregations can invite a preacher to work with them without elders. This is seen in the fact that preachers were involved in getting elders appointed in congregations (Titus 1:5; Acts 14:23).
There is some debate whether deacons can be appointed without elders in a congregation. I haven't found a satisfactory argument against it and I have found some hints that deacons might have served independently of an eldership. Men cannot be appointed who do not meet the qualifications (I Timothy 3:8-13) and they only serve in the task appointed them, such as keeping the treasury for the congregation.
A congregation cannot appoint men to oversee the congregation who do not qualify as elders (I Timothy 3:1-7; Titus 1:5-9). When a congregation as never had elders, it should be clear that at some point men will be appointed to serve as elders. Thus leaders will be appointed where elders have not currently been present.