Heating (+/-)-6,8,14,17-tetrahydro-7H-[1,2,5]triazepino[3,2-b:7,1-b']diquin
azoline-14,17-dione 1 with (+)-CSA gives (-)-1 with > 90% ee via a crystall
isation-induced asymmetric transformation, the first non-racemic example of
a C-2 symmetric bisheterocycle which is atropisomeric by virtue of retarde
d rotation around an N-N bond.