Structural parameters.
| Ring size n | N1 ΔΣθa | C2 ΔΣθa | C2 Δδb | N3 ΔΣθa | C4 ΔΣθa | C4 Δδb |
|---|---|---|---|---|---|---|
| —c | 1.2 | 0.0 | 0.0d | 0.1 | 0.0 | 0e |
| 10f | 2.9g | 0.0 | −0.9 | 2.4 | 0.2 | 4.6 |
| 9h | 2.1g | 0.0 | −3.9 | 4.6 | 0.1 | 1.3 |
| 8i | 2.1 | 0.0 | −5.9 | 13.4 | 0.0 | 0.6 |
a
ΔΣθ = deviation from planarity = 360° – sum of bond angles.
b
Δδ = Change in chemical shift from the average value of 2 representative hydantoins.
c
Values for representative monocyclic hydantoins (structures given in ESI) taken from ref. 37–40.
d
δ = 155.3 ppm (average of 2 values37).
e
δ = 173.7 ppm for iminohydantoins only (average of 2 values37).
f
Data taken from X-ray crystal structures of 11g and 18a.
g
Excluding structures where this atom lies at a ring junction.
h
Data taken from X-ray crystal structures of 4, 11a, 11f.
i
Data taken from X-ray crystal structures of 2a, 2f, 2g.