Reaction of trialkyl-(3-aminopropyl)silanes with formaldehyde and elemental sulfur

N-(3-Trialkylsilylpropyl)formamides (II) and N,N′-bis(3-trialkylsilylpropyl)thioureas (III), together with a small amount of the trialkyl-(3-isothiocyanatopropyl)silane, are formed when trialkyl-(3-aminopropyl)silanes are reacted with formaldehyde and sulfur in aqueous-ethanol medium. 1,3,5-Tris(trialkylsilylpropyl)hexahydrotriazines are the intermediate products in these reactions.