Synthetic studies on indole alkaloids. III. Synthesis of 1-ethylindolo[2,3-a]quinolizidin-2-one
作者:Mario Rubiralta、Anna Diez、Cristina Vila
DOI:10.1016/s0040-4039(00)97469-0
日期:——
The synthesis of 1-ethylindolo[2,3-a]quinolizidin-2-one 3 is reported by potassium tert-butoxide cyclization of N-hydroxyethyl-2-[1-(phenylsulfonyl)-3-indolyl]-4-piperidone ethylene acetal 10 followed by acid treatment of the intermediate spiroindolenines 8.
The synthesis of 1-ethylindolo[2,3-a]quinolizidin-2-one (1) by the intramolecular cyclization of protected N-(2-hydroxyethyl)-2-[1-(phenylsulfonyl)-3-indolyl]-4-piperidone 15 by the action of K(t)BuO and further acid treatment is reported. The methodology has been first carried out for its deethyl analogue 2 from (hydroxyethyl)piperidine 14 and has shown to be a good general method to reach indolo[2,3-a]quinolizidin-2-one systems. Compound 1 has also been obtained by an unusual rearrangement in acidic medium of 7-ethylhexahydropyrido[1',2':1,2]pyrazino[4,3-a]indole.