Abstract
The reaction of 3-(thienyl)propargylamines with maleic anhydride, followed by a domino
sequence involving successive acylation/[4+2] cycloaddition steps, leads to the formation
of the thieno[2,3-f]isoindole core. The key step, the intramolecular didehydro-Diels–Alder (IMDDA) reaction,
proceeds with a high level of selectivity, yielding the target products – 7-oxo-5,6,7,8-tetrahydro-4H-thieno[2,3-f]isoindole-4(8)-carboxylic acids – in good yields. X-ray analysis and DFT calculations
have revealed that the key step, the IMDDA reaction, proceeds via an exo transition allene state, resulting in the exclusive formation of a single isomer
of the target heterocycle.
Key words
intramolecular didehydro-Diels–Alder reaction - propargylamine - IMDDA reaction -
thieno[2,3-
f]isoindole - thiophene - thienylacetylene