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Investigations into the biosynthesis of porphyrins and corrins—calculations on 1,3‐allylic strain and [1,5]‐sigmatropic rearrangements in pyrroles, furans, and thiophenes
Author(s) -
Tietze Lutz F.,
Schulz Gerhard
Publication year - 1997
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19970030407
Subject(s) - allylic rearrangement , sigmatropic reaction , chemistry , cyclopentadiene , ab initio , stereoselectivity , ring strain , ab initio quantum chemistry methods , stereochemistry , computational chemistry , methyl group , medicinal chemistry , ring (chemistry) , molecule , organic chemistry , group (periodic table) , catalysis
The [1,5]‐sigmatropic rearrangements of hydrogen and other groups, such as methyl, tert ‐butyl, allyl, benzyl, and azafulvenium, in pyrroles and, to some extent, in furans and thiophenes, has been studied by using semiempirical and ab initio methods. These systems are used as models to explain the ring D inversion in the biosynthesis of uroporphyrinogen III and the stereoselective shift of a methyl group in the biosynthesis of vitamin B 12 . The difference in energy between the competing pathways of hydrogen and methyl shifts is significantly lower than for cyclopentadiene. The rearrangements are usually concerted, except for in strongly resonance‐stabilized systems, such as azafulvenium cations. Furthermore, ab initio calculations of the 1,3‐allylic strain for a range of substituted pyrroles has been performed, and the results compared with semiempirical data.