Compounds of the formula I R7''N--R6 RS--C,N--R4 H C, R'/I R, 3 R 2 (I) in which R, is an aromatic or heteroaromatic radical which is capable of absorbing light in the wave-length range from 200 nm to 650 nm and which is unsubstituted or substituted one or more times by C,--C,8alkyl, C2-C,ealkenyl, C2-C,8alkynyl, C,--C,ehaloalkyl, NO2, NR,OR, CN, OR,2, SR,2, C(O)R,3, C(O)OR,4, halogen or a radical of the formula II R.about.--N' R6 1 R5-C,N.R4 H I C--R3 I R2 (II) and which on absorption brings about a photoelimination which leads to the generation of an amidine group, R2 and R3 independently of one another are hydrogen, C,--C,ealkyl or phenyl which is unsubstituted or is substituted one or more times by C,--C,8alkyl, CN, OR,2, SR,2, halogen or C,--C,ehaloalkyl; R5 is C,--C,ealkyl or NR8R9; R4, R6, R, R8, R9, R,o and R independently of one another are hydrogen or C,--C,8alkyl; or R4 and R6 together form a C2-C,2alkylene bridge which is unsubstituted or is substituted by one or more C1-C4alkyl radicals; or R5 and R, independently of R4 and R6, together form a C2-C,2alkylene bridge which is unsubstituted or is substituted by one or more C1-C4alkyl radicals; or, if R5 is a radical NR8R9, R, and R9 together form a C2-C,2alkylene bridge which is unsubstituted or is substituted by one or more C1-C4alkyl radicals; and R,2, R,3 and R,4 independently of one another are hydrogen or C,--C,ealkyl; are suitable as photoinitiators for compounds which react under base catalysis.