A reaction product containing a non-cyclic alkoxy-functional polysiloxane is produced by heating a reaction system, which contains a cyclic polyorganosiloxane of the formula [(R12SiO)2/2]n, where the subscript n is an integer of at least 4 and each R1 is an alkyl group or aryl group; a silane of the formula R2(4−m)Si(OR3)m, where the subscript m is an integer from 1 to 4, each R2 independently is an alkyl group or aryl group, a hydrocarbyl group or a halogenated hydrocarbyl group and each R3 independently is an alkyl group; and a catalyst system comprising a metal trifluoromethanesulfonate of the formula [M]+[CF3SO3]−, where M is a metal atom selected from sodium (Na) and potassium (K), and a Brønsted acid, wherein Brønsted acids having a pKa≤3.0, preferably having a pKa≤2.0, particularly preferably having a pKa≤−0.0 are used.