Do I need to repeat the subject?

[Laztana]

Hello,

Since it is a long sentence, do I have to write "it" before the second verb or can I just leave it without writing the subject?

The procedure afforded moderate to good yields of target N-arylated amino acids but (it) required a significant excess...

Thanks in advance

 

[dn88]

To me, the sentence sounds good without the "it".

 

[bibliolept]

Within your example, I would not use it.
Note that if you do use "it," you should insert a comma between "acids" and "but."

 

[Laztana]

Thank you very much dn88 and bibliolept ,

I thought I could omit the "it" but I wasn't sure given the length of the sentence.