Introduction to Chemical Pharmacology, Moscow, 1959; d) US Pat, Plant Cell Physiol Z. Lehanine, B. Boutevin, vol.848, pp.841-848, 1973. ,
Synthesis (Stuttg), Russ. Chem. Rev. European J. Org. Chem. Justus Liebigs Ann. Chem. Justus Liebigs Ann. Chem. J. Org. Chem. Däbritz, Angew. Chemie Int. Ed. English Chem. Ber. Chem. Rev. J. Am. Chem. Soc. Chem. Sci. J. Org. Chem, vol.132, issue.7, pp.382-388, 1955. ,
4550-4557; f) for a review on the mechanistic aspects of guanidine-catalyzed reactions, see, Org. Biomol. Chem. Chem. Commun, vol.9, issue.51, pp.8210-8222, 2011. ,
[7] Note that the basicity of TBD and Me-TBD are similar as the protonation of the nitrogen atom is characterized by pKas of 26 and 25.4 in acetonitrile, respectively, J. Org. Chem. Inorg. Chem, vol.70, issue.46, pp.676-686, 2005. ,
[13] The hypothesis of an auto-catalytic reaction implying an isourea as a proton shuttle was also ruled out due to a high barrier, b) M. Hiraoka, in Stud line with the experimental results, pp.1250-1260, 1975. ,