SYNTHESIS OF SPIRO[2H-INDOLE-2,1'-1H-ISOINDOLE]-3,3'-DIONES, SPIRO[1H-ISOBENZOFURAN-1,2'-2H-INDOLE]-3,3'-DIONES AND SPIRO[BENZOFURAN-2,1'-ISOBENZOFURAN]-3,3'-DIONES VIA TRANSANNULAR REACTIONS OF 8 MEMBERED RING INTERMEDIATES

An auto oxidation-rearrangement product 4 was isolated from a high dil ution reaction of ninhydrin with 3,4,5-trimethoxyaniline in water. A g eneral synthesis of this compound and its derivatives 4-6 was devised by oxidation of tetrahydroindeno[1,2-b]indol-10-ones 1-3 with sodium p eriodate to give isoindolo[2,1-a]-indole-6,11-diones 4-6 in good yield . Compounds 4-6 can be easily transformed into spiro[1H-isobenzofuran- 1,2'-2H-indole]-3,3'-diones 8-10, spiro[2H-indole-2,1'-1H-isoindole]-3 ,3'-diones 11-13 and isoindole[1,2-a:2',1'-b]pyrimidine-5,15-diones 15 , 16 in high yields. Analogous reactions were performed on -5a,10a-dih ydroxybenzo[b]indeno[2,1-d]furan-10-one (17) to give a dibenzoxocintri one 18, spiro[benzofuran-2,1'-isobenzofuran]-3,3'-dione 19 and an isoi ndol-1-one 20.