Urea, thiourea and some N′‐alkyl(di)substituted ureas and thioureas were found to react as the amine component in Mannich‐type condensation reactions with p‐toluene‐ or phenylmethane‐sulfinic acid and aldehydes. Mono‐ or di‐alkylation products are formed in good yields depending on the N′‐ and N′‐substituents in the substrate, while N,N,N′‐trimethylurea or ‐thiourea failed to react. N′‐Hydroxy‐N′‐phenylthiourea is alkylated on the N′‐atom bearing the OH‐substituent as demonstrated by the ESR spectrum of the thioacyl nitroxide derived from the condensation product. Thiobenzamide, in contrast with thioacetamide, also condensed with p‐toluenesulfinic acid and formaldehyde or N′‐butyraldehyde. With benzaldehyde, however, Mannich‐type condensation did not occur and 3,5‐diphenyl‐1,2,4‐thiadiazole was isolated instead. The NMR spectra of several urea and thiourea condensation products provided evidence for hindered internal rotation in the urea and thiourea function and some ΔG≠ values for the exchange process were estimated. Intramolecular shielding effects were observed in the NMR spectrum of 4c and 4f indicating the occurrence of folded conformations.

Die Na‐Salze (I) reagieren mit den Aldehyden (II) und den Harnstoffen (III) in Wasser oder HzO/Äthanol in Gegenwart von Ameisensäure zu den Kondensationsprodukten (IV).

Aus der Dikalium‐Verbindung des Cyclooctatetraens (I) und den Cyclopentadienyltitanchloriden (II) oder aus (I) und einem Gemisch von Titan(IV)‐chlorid und Cyclopentadienyl‐natrium (V) wird die Verbindung (III) in 22‐60%iger Ausbeute erhalten.