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In the search for tricarbaporphyrinoids, a three-component acid-catalyzed condensation of azulene, 2,5-bis[( p-tolyl)hydroxymethyl]thiophene, and an aryl aldehyde has been elaborated, affording the appropriate thiatriazuliporphyrinogens. The subsequent oxidation yielded a rare example of a macrocyclic organic tetracation, which can be readily and reversibly converted into macrocyclic tri- and dicarbocations by addition of one or two hydroxides bound at the meso position(s). Further insight into the influence of carbocation formation on the geometry, electronic structure, and magnetic manifestation in 1H NMR spectroscopy has been obtained by using density functional theory calculations. The charge distribution was evaluated by mapping electron density surfaces with electrostatic potential (ESP). [ABSTRACT FROM AUTHOR]

A diazonium ion derived from 18-aminoandrostane rearranged upon decomposition by a carbonium and a carbenium ion to furnish a mixture of a cyclopropanated compound and two D- homo-androstenes. Hydrogenation of this mixture gave the saturated hydrocarbons, 18- nor- D- homo-androstane and 5α,14β-androstane, which are both fossil sterane biomarkers in Neoproterozoic crude oil. The so far unknown constitution and configuration as well as the geochemical genesis were established by this experiment. The starting material for this investigation, 18-aminoandrostane, was prepared in twelve steps from androstan-17-one (12.5 % overall yield) with a Barton reaction as the key step. [ABSTRACT FROM AUTHOR]