Alkyl derivatives fundamental properties

The results of the electrochemical investigations [4] correlate well with some fundamental properties of the heterocycles non-anellated unsaturated NHC (Ic) exist as monomers even with small A -alkyl substituents [5], while benzoanellated NHC (2c) require bulkier groups like neopentyl to be persistent or even distillable [6], otherwise dimerization or a monomer-dimer equilibrium are observed [7]. Naphtho[b]- and in particular pyrido[b]-anellated NHC, 4c and 3c, are somewhat less stable than 2c- The A, N -dineopentyl derivatives, imambiguously characterized by C NMR data (Table 2), are persistent at ordinary temperatures but decompose during attempts at high-vacuum distillation or recrystallization [8]. 

The remarkable properties of these triaryl- and diarylcyclopropenyl ions strongly supported the idea that these cations are fundamental aromatic systems and that the synthesis of derivatives free of phenyl groups should be possible. Indeed, it was soon shown that stable cations bearing only simple alkyl groups could be prepared. For... 

---