The structure of 1 Corinthians is challenging. Here is a suggestion for starters trying to follow the train of thought through chapters 4-6. It seems to me that there is a lot of stepwise parallelism rather than chiasmus. SRP
A: THE ECCLESIA SHOULD DEAL WITH THE PROBLEM OR PAUL WOULD HAVE TO.
A. 4:18 Now some are puffed up, as though I would not come to you.
B.4:19 But I will come to you shortly, if the Lord will,
C1. 4:19 and will know, not the speech of them which are puffed up, but the power.
C2. 4:20 For the kingdom of God is not in word, but in power.
A’. 4:21 What will ye? shall I come unto you with a rod, or in love, and in the spirit of meekness?
Part 2: THE SPECIFICS OF THE CASE OF IMMORALITY.
2A. 5:1-2 It is reported commonly that there is fornication among you, and such fornication as is not so much as named among the Gentiles, that one should have his father’s wife. And ye are puffed up, and have not rather mourned, that he that hath done this deed might be taken away from among you.
2B. 5:3 For I verily, as absent in body, but present in spirit, have judged already, as though I were present, concerning him that hath so done this deed,
2C. 5:4 In the name of our Lord Jesus Christ, when ye are gathered together, and my spirit, with the power of our Lord Jesus Christ,
2A’. 5:5 To deliver such an one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.
Note: 2A/2B/2C/2A’ above appear to run in parallel as a set with A/B/C/A’ which focus on – the puffed up attitude of the Corinthians, the presence of Paul physically or in spirit, the power of the Lord, and the judgment that will be made.
3A.5:6 Your glorying is not good. Know ye not that a little leaven
leaveneth the whole lump?
3B. 5:7 Purge out therefore the old leaven,
3C. 5:7 that ye may be a new lump, as ye are unleavened.
3D 5:7 For even Christ our passover is sacrificed for us:
3B’. 5:8 Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness;
3C’. 5:8 but with the unleavened bread of sincerity and truth.
4A. 5:9 I wrote unto you in an epistle not to company with fornicators:
4B. 5:10 Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then must ye needs go out of the world.
4C. 5:11 if any man that is called a brother be a fornicator, or covetous, or an idolater, or a railer, or a drunkard, or an extortioner; with such an one no not to eat.
4B1′. 5:12 For what have I to do to judge them also that are without?
4C’. 5:12 do not ye judge them that are within?
4B2’. 5:13 But them that are without God judgeth.
4A’. 5:13 Therefore put away from among yourselves that wicked person.
Note; in this section 4A,B, and C repeat the nature of the sin that had come into the ecclesia from the world. 4B’C’B’ and A’ emphasise judgment and who would bring it about.