Friedel Crafts reaction on [2,3]oxopolymethelene indoles

2421-24241-Oxo-1,2,3,4-tetrahydrocarbazoles 1a-e and 1-oxo-1,2 ,3,4,5,10- hexahydrocyclohept[b] indoles 1f-j are treated with a mixture of glacial acetic acid and polyphosphoric acid in an expectation to yield 5,6-dihydro-2-methyl-4-oxopyrano[2,3-a]carbazoles 2a-e and 5,6,7,12-tetrahydro-2-methyl-4-oxopyrano[2',3';7,6]cyclohept[b]indoles 2f-j, respectively. Instead, acetyl derivatives of 1a-j are obtained.Their characterization and the effect of the substituents on the reactivity and orientation of the above reaction have been discussed