211743-98-5Relevant academic research and scientific papers
Isoquinolinium N-arylimides and acetylenic dipolarophiles; cycloadducts and their rearrangements
Bast, Klaus,Durst, Tony,Huber, Helmut,Huisgen, Rolf,Lindner, Klaus,Stephenson, David S.,Temme, Robert
, p. 8451 - 8468 (1998)
Dimethyl acetylenedicarboxylate, methyl propiolate, and ethyl phenylpropiolate surpass the corresponding ethylenic carboxylic esters in dipolarophilic activity vs. isoquinolinium N-arylimides, a class of azomethine imines. The cycloadducts contain a N(β)-vinylphenylhydrazine system and enter into a Fischer indole synthesis which stops one step short of the indole. The [3.3]-sigmatropic rearrangement involved is likewise faster for the cycloadducts of acetylenic dipolarophiles than for ethylenic ones and does not require acid catalysis; in some cases the initial adduct escapes 1H NMR observation. The products 11-17, obtained with ethyl phenylpropiolate, provide beautiful NMR models for steric interaction of ben ring E and the 12-phenyl group. On treatment with strong acid, the pentacyclic rearrangement products suffer fragmentation; e.g., 11 furnishes 4-(o-aminophenyl)-isoquinoline and methyl benzoylacetate in methanolic HCl.
