George M. Iskander

Effect of Substituents on the Retention in HPLC Chromatography of Strychnine Derivatives

Abstract The capacity factork, relative retentions αSP and log αSP values measured on μPorasil columns for 33 strychnine derivatives using CHCl3:MeOH (containing ca 2% NH4OH) (93:7) as eluent in normal-phase chromatography. The results allow for the estimation of the effect of various substituents on the retention of these alkaloids.

Solutions in selenic acid. Part 9. Higher acids of selenic acid; the SeO3–H2SeO4 system

The SeO3–H2SeO4 system has been studied cryoscopically. A maximum freezing point of 18.84 ± 0.01 °C indicated the existence of diselenic acid H2Se2O7. Self-dissociation in diselenic acid is discussed and the presence of triselenic acid is predicted. The acidity function (HO) of SeO3–H2SeO4 solutions increases with progressive increase of SeO3 content and a value of –12.77 is reported for 68% SeO3 solution.

1,3-Dipolar character of six-membered aromatic rings. Part 56. The cycloadditions of acetylenes and 3-oxidopyridinium betaines

Cycloaddition of dimethyl acetylenedicarboxylate with a variety of 1-substituted 3-oxidopyridinium betaines yields novel furan cycloadducts. Methyl phenylpropiolate reacts similarly with the activated 1-[1′,2-di(p-nitrophenyl)vinyl]-3-oxidopyridinium betaine, but phenylacetylene adds to activated betaines to give azabicyclo[3.2.1]octene adducts.

An unusual furan cycloadduct from N-phenylbetaine and dimethyl acetylenedicarboxylate. The crystal and molecular structure of dimethyl 5-(3-N-phenyliminoprop-1-enyl)furan-2,3-dicarboxylate

Cycloaddition of dimethyl acetylenedicarboxylate with betaines such as 1-phenyl-3-oxidopyridinium does not yield the expected bicyclic product; instead, addition occurs at the exocyclic oxygen atom and ring carbon 2 of the betaine, with concomitant opening of the pyridine ring.