Interactions between Functional Groups Part IV. The responses of four diazonium groups to adjacent electron-rich atoms in peri-substituted naphthalene and quinoline derivatives
✍ Scribed by John D. Wallis; Robert J. C. Easton; Jack D. Dunitz
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- German
- Weight
- 735 KB
- Volume
- 76
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Four peri-substituted naphthalene-1-diazoniurn cations all show short attractive interactions between an electron-rich atom of the peri-substituent and the a-N-atom of the diazonium group. These are interpreted as models for incipient nucleophilic attack on a N r N bond. The diazonium group is a better acceptor of electron density 'through space' than the NO2 group, which parallels their relative 'through-u-bond' inductive effects.
Introduction.
-The diazonium group is the most electron-deficient of the common functional groups encountered in organic compounds and exerts very strong inductive and mesomeric effects [ 11. Not surprisingly, aromatic diazonium salts undergo nucleophilic addition reactions at the p-N-atom with anions such as thiolate and cyanide to yield ( Z )and (E)-l,2-diazenes . In contrast, addition to the a -N-atom would produce unstable 1,l-diazenes which decompose readily with loss of N, gas [3]. The optimal reaction coordinate for attack of a nucleophile on a triple bond has been a subject of debate [4] [5]. Indications of the preferred approach geometry may be detectable in the structures of molecules in which prototypes of the reacting groups can interact through space, as has been demonstrated for nucleophile/C=O group interactions . With this in mind, we have measured the low-temperature crystal structures of four 8-substituted naphthalene-1-diazonium cations 1 4 (as their tetrafluoroborate salts), in which an electron-rich atom (0, S , or N) belonging to the peri-substituent interacts with the electrophilic N-N bond.