Thermal cyclisation reactions of methyl 2-(pyrrol-1-yl)cinnamate and methyl 3-(1-phenylpyrrol-2-yl) propenoate

Abstract

Flash vacuum pyrolysis (FVP) of the pyrrolylcinnamate derivative 3 gives the pyrrolo[1,2-a]quinoline 10, the pyrrolo[2,1-a]isoindole 13 (R = Me) and the benzindoles 14 and 15, all in low yield, whose structures were determined by NMR methods. The isomeric precursor 4 cyclises efficiently under the same conditions to give the pyrrolizin-3-one 16.

Transition-Metal-Free, Atom- and Step-Economic Synthesis of Aminoketopyrrolizines from Benzylamine, Acylethynylpyrroles, and Acylacetylenes

“…In addition, functionalized pyrrolizines are key building blocks in the synthesis of various heterocyclic compounds. , The most popular routes for the synthesis of functionalized pyrrolizines involve multistep reactions, mainly the intramolecular cyclization of N- or C-substituted pyrrole derivatives …”

Photochemical Cycloisomerizations via 7-exo-dig Reactions on a Calix[4]arene Scaffold

“…The first is an “exited state intramolecular proton transfer” (ESIPT) 16 to form the zwitterionic-type intermediate “ B ”. In this case, an intramolecular proton transfer has undergone a 1,8-hydrogen shift . Covalent bond formation in B produces intermediate “ C ” presumably formed via a rapid E / Z isomerization.…”

“…In this case, an intramolecular proton transfer has undergone a 1,8hydrogen shift. 17 Covalent bond formation in B produces intermediate "C" presumably formed via a rapid E/Z isomerization. A second possible mechanism leading to this same putative intermediate C involves an "excited state intramolecular electron transfer" (ESIET) 18 between a phenolic hydroxy group and the triple bond (as an electron acceptor) to produce the ionic diradicals as depicted in structure "D".…”