Indazoles Indenes

H- 1.2-Benzodiazepine (1) is converted into a mixture of 3-vinyl-l//-indazole and indene in reluxing xylene.123... 

Replacement of one or more of the C or N atoms of the indole nucleus by atoms of N, C, O or S will result in dialkyltryptamine analogs some of which are very likely to be psychedelic. Among the indole analogs are isoindole, indene, indazole, diazindoles, benzo-furan, benzothiophene and benzimidazole. The syntheses of several such compounds follows. 

Indanes, chromium tricarbonyl complexes, 5, 246 Indazoles, in copper-catalyzed lead reactions, 9, 409 Indenes, chromium tricarbonyl complexes, 5, 246 Indenide derivatives, alkali compounds, 2, 13 Indenones, via imine carbonylation, 10, 136 Indenyl-alkoxo complexes, with Ti(IV), 4, 500 Indenyl-amido complexes, with Ti(IV), 4, 454 Indenyl-amido dimethyl complexes, with Ti(IV), 4, 442 Indenyl bridges, in [Pg.126]

UV irradiation of 2,5-diphenyloxadiazole (43) together with benzo[6]thiophene (42) yields an oxadiazepine (44) as the initial and major product, along with the 3-substituted benzo[6]thiophenes (45a) and (45b). These latter products are also obtained on photolysis of the oxadiazepine (Scheme 6). Prolonged irradiation gives products (45) and what is formally a trans [2 + 2] cycloadduct (46). This cycloadduct is also formed from oxadiazole (43) and benzo[6 jthiophene on irradiation with benzophenone as a sensitizer and the reaction presumably involves the triplet state of the oxadiazole. Somewhat similar photoreactions have been observed between oxadiazole (43) and methyIbenzo[6]thiophenes, indazoles, furan and indene (77BCJ3281). 

The first naphtho[a]cyclopropene 68d was also obtained by that route. 3H-indazole was proposed as an intermediate in this reaction 78>. The reaction proceeds equally well from the triplet state of 7. However with acetone light capture from the sensitizer may not have been complete. A trapping of the diradical intermediate 67 to give the known indene 69 by photolysing 7 in dimethyl-acetylene-dicarboxylate (ADC) afforded only a trace of 69. However the yield of 68a was reduced to 40%. Either trapping of 67 was not effective enough or ADC may have acted as quencher. Trapping with furan or cyclopentadiene was also not effective 78a). 

Similarly, alkane- and arenesulfonyl isocyanates gave 2-sulfonyl-2,3-dihydroisoindol-l-ones 11 with benzocyclopropene. 2,3-Dihydroisoindol-l-one was produced as a byproduct in 4% yield in the case of arenesulfonyl isocyanates. Cyclopropa[ ]naphthalene underwent addition to 4-phenyl-47/-l,2,4-triazole-3,5-dione at 20°C almost instantaneously to give an indazole 12 in 92% yield.Both reactions are believed to occur by electrophilic attack on the cyclo-proparene and may involve a zwittcrionic intermediate. When benzyne was generated from benzenediazonium-2-carboxylate in refluxing dioxane in the presence of cyclopropa[Z ]naph-thalenc, 5//-naphtho[2,5-a]indene was formed in 13% yield. 

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