Cyclisation reactions of bis-protected guanidines

The cyclisation of N-allyl- and N-homoallylguanidines using DMDO or I₂/K₂CO₂ leading to novel heterocycles is reported.     

NMR of some benzodiazepine drugs: Structure elucidation with lanthanide-induced shifts of N-1 substituted benzodiazepinones

Two 1,4-benzodiazepinones of psychopharmacological interest, pinazepam (2) and prazepam (3), were studied in solution by ¹³C and ¹H NMR. ¹H variable-temperature experiments showed that the seven-membered ring exists in a simple pseudo-boat form at room temperature, but the energy barrier is higher in 3 (ΔG_405°c = 82.8 kJ mol^?1) than in diazepam (1). Moreover, upon addition of LSR, the boat conformation is retained in the lanthanide ion-substrate complex, as with 1 in the solid state. Using a concentration-dependent shift technique and a computer-assisted LIS method, the conformations of the N-branched side-chain were investigated. Two preferred orientations were found for the propargyl group of 2, while three unequally populated conformations of the cyclopropyl moiety of 3 are distributed preferentially in the sterically unhindered space around the complex.