Chemistry Insights: Synthesis, Rearrangements, and Acids
Explore a novel synthetic route to the tricyclic core of (-)-galanthamine, learn about the Claisen Rearrangement, sigmatropic rearrangements, and the properties of various acids such as phenol and carbonic acid. Discover the significance of pKa values, understand the steric hindrance of bases like Diisopropylethylamine (DIPEA), and grasp the importance of compounds like Methoxymethyl (MOM) and 2,6-Lutidine in organic chemistry.
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Presentation Transcript
Chandrasekhar, S.; Basu, Debjit; Sailu, M.; Kotamraju, S. Novel synthetic route to the tricyclic core of ()-galanthamine. Tetrahedron Letters (2009), 50(34), 4882-4884.
pKa phenol = 9.9 pKa2 of carbonic acid = 10.33
The Claisen Rearrangment is a [3,3] sigmatropic rearrangement Aromatic Claisen Rearrangement Cope Rearrangement is related
DIPEA = Diisopropylethylamine (Hunigs Base). This base is more sterically hindered, and thus less nucleophilic, than triethylamine. pKa of the conjugate acid of Hunig s base = 11.0 MOM = Methoxymethyl MOMCl = H3C-O-CH2-Cl
2,6-Lutidine = pKa conjugate acid of 2,6-lutidine = 6.7
pKa hydroxylamine hydrochloride = 6 pKa conjugate acid of pyridine = 5.2 pKa conjugate acid of triethylamine = 10.6
pKa acetonitrile = 25 pKa phenylacetonitrile = 22 DMPU = Dimethylpropyleneurea = solvent to replace HMPA, a carcinogen LDA = lithium diisopropylamide pKa of diisopropylamine (conjugate acid of LDA) = 36
DPPA = diphenylphosphoryl azide = DBU = Diazabicycloundecene = Conjugate acid of DBU pKa = 13.2
