This invention provides a class of cyclic silylureas and a process of preparing them, which process comprises reacting a cyclosilazane with an isocyanate containing moiety; a class of cyclosilazanes and process for making them, which process comprises heating an aminoalkylalkoxysilane in the presence of a basic catalyst at a temperature less than 100.degree. C. at subatmospheric pressure; and aminoalkylalkoxysilanes and a process for making them, which process comprises reacting a nitrile and a vinylsilane while heating in the presence of a base selected from the group consisting (a) an alkali metal, (b) alkali metal alkoxide, (c) an alkali metal amide, (d) an alkali metal hydride and (e) mixtures thereof to form a reaction product which is subsequently hydrogenated.