The present invention provides compounds of formula (I) wherein R1, R2, R3, R4, n, A1, A2, A3, A4, Y1, Y2 and Y3 are as defined in the claims. The invention also relates to processes and intermediates for preparing these compounds, to insecticidal, acaricidal, nematicidal and molluscicidal compositions comprising these compounds and to methods of using these compounds to control insect, acarine, nematode and mollusc pests.