Isotopic Labeling Study of the Formation of Calix[5]pyrroles Catalyzed by Bi(NO3)3

Abstract

Abstract:One of the more elusive classes of macrocycles includes the calix[5]pyrroles, which can be obtained from pyrrole and acetone in the presence of low concentrations of Bi(NO 3 ) 3 -5H 2 O. An isotopic labeling experiment aided the proposal of a mechanism to explain the formation of calix [5]pyrrole at low acid concentrations and the exclusive formation of calix[4]pyrrole at high acid concentrations. We assume that the mechanism involves HNO 3 , which is released from the Bi salt.

Synthesis and Docking Studies of the NovelN-(2,2-Di(1H-pyrrol-2-yl)ethyl)adamantane-1-carboxamide, a Potential 11β-HSD1 Inhibitor

“…One possible explanation for the reversibility is that Bi(NO 3 ) 3 ⋅5H 2 O liberated nitric acid, as has been observed in the condensation of acetone with pyrrole in the presence of a bismuth nitrate catalyst [19]. Once the aldehyde deprotection reaction had been optimized (with a 1.5 h acetal reaction time), the pyrrane condensation was carried out in the same reaction mixture by adding pyrrole in excess.…”