Table 2. Choosing an Experimental Technique for Configurational Stability Assessment.

Technique	Favored by	Disfavored when	Compound requirement
VT-NMR: Line-shape analysis, EXSY, or kinetic analyses	Fast interconversion (t1/2 < 1 s,26 e.g., analysis of nonchromatographically separable isomer mixtures), ΔG‡ < 23 kcal/mol27	Atropisomers are enantiomers or chemically unstable at elevated temperature	∼3 mg of atropisomer mixture (or atropisomerically enriched material)
Time-course NMR	Medium-to-slow interconversion within the accessible temperature rage (t1/2 > 5 min23), ΔG‡ = 22–33 kcal/mol28	Atropisomers are enantiomers or unstable, chiral separation is not feasible	∼3 mg of atropisomerically enriched material
Chiral Chromatography (e.g., HPLC, SFC)	Slow interconversion (t1/2 > 20 min23), ΔG‡ > 24 kcal/mol	Atropisomers are rapidly converting, or chiral separation is not feasible	<1 mg of atropisomerically enriched material