Compounds of the general formula I ##STR1## in which R.sup.1 is hydrogen, C.sub.1 -C.sub.12 -alkyl, C.sub.5 -C.sub.7 -cycloalkyl, phenyl or benzyl and R.sup.2 is hydrogen or C.sub.1 -C.sub.4 -alkyl, or R.sup.1 and R.sup.2, together with the C atom to which they are attached, form a 5-membered or 6-membered ring, and R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are identical or different and are hydrogen, C.sub.1 -C.sub.12 -alkyl, phenyl which is unsubstituted or monosubstituted to trisubstituted by C.sub.1 -C.sub.4 -alkyl, halogen or C.sub.1 -C.sub.4 -alkoxy, or is a group of the formula --CH.sub.2 OR.sup.7 (II) in which R.sup.7 is C.sub.1- C.sub.12 -alkyl, phenyl which is unsubstituted or monosubstituted to trisubstituted by C.sub.1 -C.sub.4 -alkyl, halogen or C.sub.1 -C.sub.4 -alkoxy, or is --C(O)--R.sup.8, and R.sup.8 is C.sub.1 -C.sub.12 -alkyl, and also not more than two of the radicals R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are one or two groups of the formula --CH.sub.2 CH.sub.2 Si(OR.sup.9).sub.3 (III), --CH.sub.2 OC(O)CH.sub.2 Si(OR.sup.9).sub.3 (IV), --Ch.sub.2 O(C.sub.m H.sub.2m)Si(OR.sup.9).sub.3 (V) or ##STR2## in which R.sup.9 is C.sub.1 -C.sub.4 -alkyl or phenyl and m is a number from 1 to 8 and r is a number 1 or 2 and t is 0, 1, or 2 and R.sup.1 is as defined above, and, in addition, compounds of the formula I in which R.sup.4 and R.sup.5 together from a group of the formula ##STR3## in which R.sup.9 is as defined above and R.sup.3 and R.sup.6 in this case are hydrogen and n is 1 or 2 and, if n is 1, Z is an organic radical which is derived from a primary amine ZNH.sub.2 and can contain one or two --Si(OR.sup.9).sub.3 groups and, if n is 2, Z is a divalent organic radical derived from a diprimary diamine H.sub.2 NZNH.sub.2 ; subject to the proviso that the compounds of the formula I contain one to three --Si(OR.sup.9).sub.3 groups, are suitable for use as adhesion promoters, particularly for moisture-curing epoxide and polyurethane resins.