- A general method for the synthesis of N-unsubstituted 3,4-diarylpyrrole-2, 5-dicarboxylates
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A general method for the synthesis of N-unsubstituted 3,4-diarylpyrrole-2, 5-dicarboxylates (3) has been developed. The key reactions involved are the Hinsberg-type synthesis of dimethyl N-benzyl-3,4-dihydroxypyrrole-2,5- dicarboxylate (6) followed by palladium-catalyzed Suzuki-Miyaura coupling of its bis-triflate derivative (7). The N-benzyl protecting group of the resulting 3,4-diaryl pyrrole-2,5-dicarboxyl ates (8) is cleanly removed under hydrogenolytic or solvolytic conditions.
- Fukuda, Tsutomu,Hayashida, Yukie,Iwao, Masatomo
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experimental part
p. 1105 - 1122
(2010/09/16)
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- 3,4-Dialkoxypyrroles and 2,3,7,8,12,13,17,18-octaalkoxyporphyrins
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A five-step general synthesis of 3,4-dialkoxypyrroles 7c-f is described starting with the condensation of dimethyl N-benzyliminodiacetate (1 b) and diethyl oxalate to give dimethyl 1-benzyl-3,4-dihydroxypyrrole-2,5-dicarboxylate (2b), which is bis-O-alkylated to the corresponding 3,4-diethers 3c-g. Pyrrole N-benzyl cleavage followed by ester hydrolysis and decarboxylation leads to 7c-f in 10-50% overall yield. Pyrroles 7c-f react with formaldehyde or benzaldehydes to give meso-H- (8a-d) or meso-tetraaryloctaalkoxyporphyrins 9a-g in moderate yields.
- Merz,Schropp,Dotterl
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p. 795 - 800
(2007/10/02)
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