Indolo quinolizinium

A number of successful approaches to the indolo[2,3-a]quinolizinium ring system (252) (generally leading to reduced derivatives) have been reported by Swan and co-workers. By treating l-(4 -hydroxybutyl)-l,2,3,4-tetrahydro-j8-carboline (391) with hydrobromic acid followed by base, l,2,3,4-tetrahydro-12jEf-indolo[2,3- ]quinolizinium bromide... 

It is interesting to note that the 7,12-dihydro-2-methyl-6H-indolo[2,3-n] quinolizinium chloride (216) (R = acetal) can be deprotonated to give the orange-yellow zwitterion 217, whereas the vinylog amide 218 is formed when R = COMe (Scheme 71). This substitution pattern gives rise to the... 

The parent skeleton of the alkaloids containing the indolo[2,3-n] quinolizinium ring system 321 was examined spectroscopically (Scheme 99). On conversion to the deprotonated form 322 in CD3OD, all resonance frequencies shift to higher field and this tendency is particularly... 

An interesting observation has been described in Section II.C.3 (Scheme 70). 7,12-Dihydro-2-methyl-6//-indolo[2,3-u]quinolizinium chloride (214) can be deprotonated to give the orange-yellow zwitterion 215 or the vinylog amide 216 depending on the substitution pattern (Scheme 104). 

Quinolizinium ions fused with indole are related to yohimbine alkaloids flavopereirine, sempervirine, reserpine, alstoniline, ajmaline, and so on. Parent indolo[2,3-a]quinolizinium salt (272) has been reported (87TL5259). l-Phenylsulfonyl-2-(2-pyridyl)indole 271 was treated with H-butyllithium to afford the 3-lithio species, which was quenched with bromoacetalde-hyde to give the cyclization product (48%). It was dehydrated with aq. NaOH to afford 272 (89%). Using this method, sempervirine (273) was obtained (88T3195). 

The reaction of l-methyl-2-(2 -pyridyl)indole (274) with bromoacetone in acetone gave the dimethyl derivative (275) of indoloquinolizinium salt (42%). The cyclization product from 2-(2 -pyridyl)indole (276), however, was not 7-methyl-12//-indolo[2,3-a]quinolizinium salt (277), but 11-meth-ylindolo[2,1 -a]-2-azoniaquinolizinium salt (278) (34%) (64JOC3584). 

Indolo[2,3-a]pyrrolo[3,4-c)carbazole-5,7(6fl)-diones 44,946 Indolo[2,3-a]quinolizinium betaines 42,781s43... 

XII-626) hydrolysis of which gives the pyridone (XI-627) in 80%yield. Ring closure of XII-626 (X = Br) by fusion in an oil bath or by treatment of XI-627 with phosphorus oxychloride gives 6,7-dihydro-12/f-indolo[2,3-fl] quinolizinium salts (XI-628). m this series the best yields are obtained in the direct sequence XII-626 (X= Br)Xn-628... 

Indole-2-carboxylic acids, 121, 252, 254 Indole-3-carboxylic acids, 253, 254 Indolenines, 84, 167, 169 dichloromethyl-, 68 quatemization of, 39 quinolines from, 69-71 ring expansion of, 69-71 Indolizmes, formylation of, 73 Indolo[l,2-a]pyrazinone, 119 Indolo[2,3-a]quinolizinium salts, synthesis of, 178... 

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