Trifluoroacetic acid: A more effective and efficient reagent for the synthesis of 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones and 3-arylmethyl-2-amino quinolines from Baylis-Hillman derivatives via Claisen rearrangement

Trifluoroacetic acid has been discovered to be a highly effective and efficient reagent for the tandem Claisen rearrangement and cyclisation reaction to yield 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones from compounds obtained from the SN2 reaction between anilines and acetyl derivatives of Baylis-Hillman adducts of acrylates in the presence of DABCO. In contrast similar compounds obtained from the acetyl derivatives of Baylis-Hillman adduct of acrylonitrile on treatment with trifluoroacetic acid directly furnish 3-arylmethyl-2-amino-quinoline via tandem Claisen rearrangement, cylisation and isomerisation.

Synthesis of substituted 1H- and 3H-1-benzazepines: Rearrangement of 2-alkoxycarbonyl-1H-1-benzazepines to isoquinolines

The SnCl2-mediated reduction of nitro groups in 2-nitro-4-(2-nitro-benzylidene)-alkanoates and 4-nitro-2-(2-nitro-alkylidene)-alkanoates afforded via SN2′ reaction of ethyl nitroacetate and nitroethane with the acetyl derivatives of Baylis-Hillman adducts afforded by 2-nitro-substituted benzaldehydes leads to facile synthesis of substituted 1H-1-benzazepine and 3H-1-benzazepine. During the study an unprecedented rearrangement of 2-alkoxycarbonyl-1H-benzazepine to substituted isoquinoline has been observed.

An alternate approach to quinoline architecture via Baylis-Hillman chemistry: SnCl2-mediated tandem reaction toward synthesis of 4-(substituted vinyl)-quinolines

An alternate approach to densely substituted quinolines from the products of SN2 nucleophilic substitution reaction between the acetyl derivatives of the Baylis-Hillman adducts obtained from 2-nitrobenzaldehydes and the carbonyl group containing carbon nucleophiles is described. Treatment of these compounds with SnCl2, trigger a tandem reaction wherein reduction of the nitro group is followed by a remarkably regioselective intramolecular cyclization and subsequent dehydrogenation to afford 4-(substituted vinyl)-quinolines.