The Preparation and Formylation of 2-Acetamidothiophenes

Intramolecular Cyclization of Azides by Iminium Species. A Novel Method for the Construction of Nitrogen Heterocycles under Vilsmeier Conditions

“…The synthesis of quinoline framework from acylanilides is reported to be favored by employing POCl 3 and DMF in a ratio of 7:3 . However, we observed that the nature of the cyclization product of N -aryl-2-azidoacetamides was not influenced by varying the ratio of reagent mixture.…”

Heterocyclisation of trisubstituted formamidines containing an aryl or hetaryl substituent at the imine nitrogen atom

“…On treatment with excess Vilsmeier reagent, reactive aminosubstituted heterocyclic compounds are converted into formylhetarylformamidines. 43 For example, 2-aminoindole 62 was used to synthesise N 1 ,N 1 -dimethyl-N 2 -(3-formylindol-2-yl)formamidine 63. 44 Refluxing this product with ammonium salts in ethanol induces cyclisation giving rise to salt 64 the subsequent reduction of which affords 3-substituted 2,3,4,4a-tetrahydropyrimido [4,5b]indole 65.…”

Synthesis of the Fused Heterobicycles 5-Pyridin-2-yl-thieno[3,2-b]pyridine, 6-Pyridin-2-yl-thieno[2,3-b]pyridine and 6-Pyridin-2-yl-thieno[3,2-c]pyridine

“…The overall yield of this five-step synthesis was 32%. (13) was formed together with many by-products. The reduction with LiAlH 4 was attempted at different temperatures (-78°C, -10°C, 0°C), but no improvement of the yield after oxidation was achieved.…”

“…It was decided that because of the low yield and the many by-products this pathway was not worth pursuing any further and a synthesis of [3-(3-oxo-3-pyridin-2-ylpropenyl)thiophen-2-yl]carbamic acid ethyl ester (14) was never attempted. A new pathway to 2, based upon a Beckmann rearrangement, [12][13][14][15][16][17] ring closure under modified Vilsmeier reaction conditions 18,19 and a Negishi cross-coupling [20][21][22][23] was devised (Scheme 4). 18,24,25 The use of three equivalents of POCl 3 and one equivalent of DMF resulted in ring closure and 19 was obtained in a yield of 30%.…”