I cant figure out how to write a general SMARTS pattern for some cases, so for example for the simple case of a nitrogen heterocycle, we can simply have
[n,NR], but what if i am trying to match a nitrogen heterocyle that does not have an oxygen in the same cycle? I cant think of a general pattern that would work for any ring size. The only thing i can think off is to write one for each ring size like
[#7R]1@[!#8R]@[!#8R]@[!#8R]1 for a 4 membered heterocyle, but this will quickly get tedious and as mentioned not a general solution. Thanks in advance!