Unusual phlorins from the oxidative coupling of pentapyrromethanes: their facile conversion to meso-substituted porphyrins
摘要:
Direct, oxidant-mediated intramolecular coupling of pentapyrromethanes afforded 5-aryl-5-(2 ' -pyrryl)-10,15,20-triaryl-porphyrin (phlorins) as single products. The outcome of the reaction is comparable with the oxidative coupling of tetra-pyrromethanes. Treatment of obtained phlorins with trifluoroacetic acid resulted in exclusive elimination of the peripheral pyrrole affording mwso-tetraarylporphyrins quantitatively. The rate of pyrrole elimination depends on the acid concentration. The selective binding with fluoride anion was also observed with a large association constant. (C) 2001 Published by Elsevier Science Ltd.
Organocatalytic synthesis of dipyrromethanes by the addition of N-methylpyrrole to aldehydes
摘要:
The reaction of aldehydes with N-methylpyrrole carried out in the presence of catalytic pyrrolidinium tetrafluoroborate at room temperature affords the corresponding dipyrromethanes and minor amounts of tripyrranes. This new, mild, and convenient process represents the first organocatalytic synthesis of dipyrromethanes. The products are obtained in chemical yields similar to those obtained with existing methods, which, however, require either a much larger excess of heterocycle (when aldehydes are employed as starting materials), or more drastic reaction conditions (when aldehyde equivalents are used as starting materials) than those employed here. A mechanism is proposed to explain the course of this reaction. (c) 2006 Elsevier Ltd. All rights reserved.
The reaction of aldehydes with N-methylpyrrole carried out in the presence of catalytic pyrrolidinium tetrafluoroborate at room temperature affords the corresponding dipyrromethanes and minor amounts of tripyrranes. This new, mild, and convenient process represents the first organocatalytic synthesis of dipyrromethanes. The products are obtained in chemical yields similar to those obtained with existing methods, which, however, require either a much larger excess of heterocycle (when aldehydes are employed as starting materials), or more drastic reaction conditions (when aldehyde equivalents are used as starting materials) than those employed here. A mechanism is proposed to explain the course of this reaction. (c) 2006 Elsevier Ltd. All rights reserved.
Unusual phlorins from the oxidative coupling of pentapyrromethanes: their facile conversion to meso-substituted porphyrins
作者:Jae-Won Ka、Chang-Hee Lee
DOI:10.1016/s0040-4039(01)00783-3
日期:2001.7
Direct, oxidant-mediated intramolecular coupling of pentapyrromethanes afforded 5-aryl-5-(2 ' -pyrryl)-10,15,20-triaryl-porphyrin (phlorins) as single products. The outcome of the reaction is comparable with the oxidative coupling of tetra-pyrromethanes. Treatment of obtained phlorins with trifluoroacetic acid resulted in exclusive elimination of the peripheral pyrrole affording mwso-tetraarylporphyrins quantitatively. The rate of pyrrole elimination depends on the acid concentration. The selective binding with fluoride anion was also observed with a large association constant. (C) 2001 Published by Elsevier Science Ltd.