A one pot reaction involving sym 𝑁,𝑁'-diarylthiourea and the respective arylamine in the presence of aq. KOH in nitrobenzene at $≥ 105^\circ$C afforded sym 𝑁,𝑁',𝑁"-triarylguanidine in fair to good yield and the products have been characterized. Sym 𝑁,𝑁',𝑁"-tri(4-tolyl)guanidine possesses (7) anti-anti conformation, sym 𝑁,𝑁',𝑁"-tri(2-tolyl)guanidine (8) and sym 𝑁,𝑁',𝑁"-tris(2,4-xylyl)guanidine (11) each possess anti-anti $\alpha \beta \alpha$ conformation whereas sym 𝑁,𝑁',𝑁"-tris(2-anisyl)guanidine possesses (9) syn-anti $\alpha \beta \beta$ conformation as determined by single crystal X-ray diffraction data. The observed conformations appear to result from a subtle balance between steric factor associated with the aryl substituent and multiple electronic factors namely 𝑛-𝜋 conjugation/negative hyperconjugation and non-covalent interactions in the crystal lattice.
Volume 132, 2020
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