Hydrogen Bromide → HCID 15499896, compound

Participants

Reaction Conditions

Reaction Steps

Pyrromethene Hydrobromides and BF2Complexes. Crude pyrromethene hydrobromides 6 were obtained from a α-pyrrole carboxylate esters 4 (Kleinspehn, 1955) and converted without purification to P-BF2 dyes 7. A mixture of ethyl 3-phenyl-4-ethyl-5-methylpyrrole-2-carboxylate 40 (2.57 g, 10 mmol), hydrobromic acid (3 ml, 48%) and formic acid (3.5 g) was heated at 100° C. for 4 h. The reaction mixture was cooled to 0° C. to bring about the separation of crude 3,3'-diphenyl-4,4'-diethyl-5,5'-dimethylpyrromethene hydrobromide 6u 1.3 g(55%) mp 235° C. (dec); ethyl 3,4-diphenyl-5-methyl-pyrrole-2-carboxylate 4p gave crude 3,4,3',4'-tetraphenyl-5,5-dimethylpyrromethene hydrobromide 6v (75%) mp 280° C. (dec) (lit. mp 280° C. (dec)); and ethyl 3-phenyl-4-acetyl-5-methylpyrrole-2-carboxylate 4q gave crude 3,3'-diphenyl-4,4'-diacetyl-5,5'-dimethylpyrromethene hydrobromide 14 (50%) mp 230° C. (dec). In similar conversions 3,5-dimethyl-4-tert-butylpyrrole-2-carboxylate 4g gave crude 3,5,3',5'-tetramethyl-2,6-di-tert-butylpyrromethene hydrobromide 6x and ethyl 3,4-diethyl-5-methylpyrrole-2-carboxylate 4k gave crude 3,4,3',4'-tetraethyl-5,5'-dimethylpyrromethene hydrobromide 6y.

Provenance & Evidence