118361-73-2Relevant academic research and scientific papers
DIELS-ALDER REACTIVITY OF PYRANOINDOL-3-ONES. PART 2. STERIC AND ELETRONIC EFFECTS IN THE ADDITION TO ALKYNES
Moody, Christopher J.,Shah, Pritom
, p. 1407 - 1416 (2007/10/02)
The pyranoindol-3-ones (1a), prepared from ethyl 2-acetoxymethylindol-3-ylacetate (2), and (1b)-(1h), prepared from indol-3-ylacetic acid, undergo Diels-Alder reaction with dimethyl acetylenedicarboxylate to give, with concomitant loss of carbon dioxide, carbazole 2,3-diesters (7).The reactions of (1) with the unsymmetrical acetylene, ethyl propiolate, give mixtures of the carbazole 3-ester (8) and carbazole 2-ester (9), with the former predominating.The regioselectivity of the Diels-Alder reaction increases with increasing steric bulk at the 1-position of the dienes (1), although in the case of the N-ethoxycarbonyl derivative (10) regioselectivity is reversed.Reaction of the pyrone (1b) with a variety of unsymmetrical acetylenes gives mixtures of carbazoles (13) and (14), the regioselectivity of the Diels-Alder reaction being dependent on the acetylene substituents, and in some cases being regiospecific.
