Indolo quinolizinium salts

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). 

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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