Synthesis of 3,9,9,9a-tetramethyl-1,2,3,9a-tetrahydro-9H-imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]-indol-2-ones by reaction of 2,3,3-trimethyl-3H-indole with 2-bromopropionamides

Alkylation of 2,3,3-trimethyl-3H-indole with 2-bromopropionamide and the subsequent treatment of the formed 1-(1-carbamoylethyl)-2,3,3-trimethyl-3H-indolium bromide with a base afforded 3,9,9,9a-tetramethyl-1,2,3,9a-tetrahydro-9H-imidazo1,2-a]indol-2-one. Condensation of the 1-(1-carbamoylethyl)-2,3,3-trimethyl-3H-indolium salt with 2-hydroxy-1-naphthaldehyde gave a mixture of diastereomeric 1-(1-carbamoylethyl)spiro2H-indole-2,3-3H]naphtho2,1-b]pyrans].Published in Khimiya Geterotsiklicheskikh Soedinenii, No 11, pp. 1690–1694, November, 2004.