A compound of the general formula or a salt or solvate thereof, wherein A 1 is selected from the group consisting of N and C-R 8; A 2 is selected from the group consisting of N and C-R 3; A 3 is selected from the group consisting of N and C-R 9; A 4 and A 5 and A 6 are independently selected from the group consisting of N and C-R 1; R 1 is selected from the group consisting of hydrogen, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl, (C 2 -C 3)alkynyl, halogen, (C 1 -C 3)alkoxy, and (C 1 -C 3)haloalkyl; R 2 is selected from the group consisting of hydrogen, halogen, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl and (C 2 -C 3)alkynyl; R 3 is selected from the group consisting of hydrogen, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl, (C 2 -C 3)alkynyl, NR 4 R 5, (C 1 -C 3)alkyl-NR 4 R 5, (C 2 -C 3)alkenyl-NR 4 R 5, (C 2 -C 3)alkynyl-NR 4 R 5 and cyano, wherein R 4 and R 5 are independently selected from the group consisting of hydrogen, (C 3 -C 5)cycloalkyl, (C 3 -C 5)heterocycloalkyl, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl and (C 2 -C 3)alkynyl, or R 4 and R 5 together with the nitrogen atom to which they are attached form a 5- to 7-membered heterocyclic ring optionally comprising in addition to the aforementioned nitrogen atom a further heteroatom group selected from the group consisting of O and NR 6, wherein R 6 is selected from the group consisting of hydrogen, methyl, acetyl and formyl; Y is selected from the group consisting of O and S; R 8 is selected from the group consisting of (C 1 -C 4)alkyl, (C 2 -C 4)alkenyl, (C 2 -C 4)alkynyl, (C 3 -C 5)cycloalkyl and (C 3 -C 5)heterocycloalkyl; R 9 is selected from the group consisting of hydrogen, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl, (C 2 -C 3)alkynyl, and (C 1 -C 3)alkoxy; wherein alkyl, alkenyl or alkynyl may be independently substituted with one or more (C 1 -C 3)alkoxy groups; and wherein cycloalkyl or heterocycloalkyl may be independently substituted with one or more (C 1 -C 3)alkoxy, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl or (C 2 -C 3)alkynyl groups, with the proviso that the following compounds are excluded: 3-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 2,3,9-trimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3,9-dimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 2,3-dimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-ethyl-9-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-(tert-butyl)-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-(tert-butyl)-9-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, and 2-methyl-8-phenyl-6H-chromeno[6,7-d]oxazol-6-one. A 1 is selected from the group consisting of N and C-R 8; A 2 is selected from the group consisting of N and C-R 3; A 3 is selected from the group consisting of N and C-R 9; A 4 and A 5 and A 6 are independently selected from the group consisting of N and C-R 1; R 1 is selected from the group consisting of hydrogen, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl, (C 2 -C 3)alkynyl, halogen, (C 1 -C 3)alkoxy, and (C 1 -C 3)haloalkyl; R 2 is selected from the group consisting of hydrogen, halogen, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl and (C 2 -C 3)alkynyl; R 3 is selected from the group consisting of hydrogen, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl, (C 2 -C 3)alkynyl, NR 4 R 5, (C 1 -C 3)alkyl-NR 4 R 5, (C 2 -C 3)alkenyl-NR 4 R 5, (C 2 -C 3)alkynyl-NR 4 R 5 and cyano, wherein R 4 and R 5 are independently selected from the group consisting of hydrogen, (C 3 -C 5)cycloalkyl, (C 3 -C 5)heterocycloalkyl, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl and (C 2 -C 3)alkynyl, or R 4 and R 5 together with the nitrogen atom to which they are attached form a 5- to 7-membered heterocyclic ring optionally comprising in addition to the aforementioned nitrogen atom a further heteroatom group selected from the group consisting of O and NR 6, wherein R 6 is selected from the group consisting of hydrogen, methyl, acetyl and formyl; Y is selected from the group consisting of O and S; R 8 is selected from the group consisting of (C 1 -C 4)alkyl, (C 2 -C 4)alkenyl, (C 2 -C 4)alkynyl, (C 3 -C 5)cycloalkyl and (C 3 -C 5)heterocycloalkyl; R 9 is selected from the group consisting of hydrogen, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl, (C 2 -C 3)alkynyl, and (C 1 -C 3)alkoxy; wherein alkyl, alkenyl or alkynyl may be independently substituted with one or more (C 1 -C 3)alkoxy groups; and wherein cycloalkyl or heterocycloalkyl may be independently substituted with one or more (C 1 -C 3)alkoxy, (C 1 -C 3)alkyl, (C 2 -C 3)alkenyl or (C 2 -C 3)alkynyl groups, with the proviso that the following compounds are excluded: 3-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 2,3,9-trimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3,9-dimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 2,3-dimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-ethyl-9-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-(tert-butyl)-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-(tert-butyl)-9-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, and 2-methyl-8-phenyl-6H-chromeno[6,7-d]oxazol-6-one. 3-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 2,3,9-trimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3,9-dimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 2,3-dimethyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-ethyl-9-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-(tert-butyl)-5-phenyl-7H-furo[3,2-g]chromen-7-one, 3-(tert-butyl)-9-methyl-5-phenyl-7H-furo[3,2-g]chromen-7-one, and 2-methyl-8-phenyl-6H-chromeno[6,7-d]oxazol-6-one.