Synthesis and thermal rearrangement of 2-allyl substituted 2-pyrrole derivatives

One-Pot Synthesis of Unprotected 2-Acylpyrroles from 1,2,3-Triazoles and 2-Hydroxymethylallyl Carbonates

“…Using 6b with a dimethyl substituent at the 3-position as substrate, the elimination and isomerization reactions proceeded efficiently to afford the 3H-pyrrole 7c in 82% yield (Scheme (2)). Notably, considering the previous reports on rearrangements of 2H- and 3H-pyrroles to thermodynamically more stable 1H-pyrroles via [1,5]-sigmatropic -Me shift, etc., the developed DBU-promoted domino process could be applied to the synthesis of biologically important pyrrole isomers . Based on the current observations and previous reports, , the reaction mechanism involving E1cB elimination, isomerization, and aromatization sequence is proposed (Scheme B).…”

The synthesis and chemistry of azolenines. Part 2. A general synthesis of pyrrole-2-carboxylic acid derivatives by the reaction of 2H-azirines with enamines, and the crystal and molecular structure of ethyl 3-phenyl-4,5,6,7-tetrahydroindole-2-carboxylate

“…The Nature of the Intermediate 1 : 1 Adduct.-L'abbe and co-workers proposed that the initial adduct of type (4) ringopened to a 2,5-dihydropyrrole of type (11) (Scheme 3) prior to loss of the secondary amine. 13 We believe that the bicycles (4) are instead converted into a mixture of a 2,3-dihydropyrrole (12) and a 3,4-dihydropyrrole (13), possibly in equilibrium, and with the former being the major (>75%) component. Liquid film i.r.…”

“…Liquid film i.r. spectra for a series of intermediates having R4 = Ph and R5 = COrMe show common peaks at 1 746w [vcr0 of (13)], 1 685vs [vcz0 of (12) but not (ll)], 1 545s (somewhat broad), 1 385s, 1 270s, and 1 120s cm-'. There is only weak absorption in the NH region.…”