Under what circumstances can the stereochemistry at nitrogen atom be faithfully retained and identified?
Because in most cases nitrogen atoms tend to undergo stereorandomisation by flipping due to its lone pair. I know of one example which has a three membered ring where nitrogen flips very slowly due to the high s character in the lone pair which requires significant activation energy to flip. But I wanted to know of the other cases where this is possible (probably in a stereo locked system inhibiting flipping).