307002-75-1Relevant academic research and scientific papers
endo-selective intramolecular Pauson - Khand reactions of γ-oxygenated-αβ-unsaturated phenylsulfones
Adrio, Javier,Rivero, Marta Rodrguez,Carretero, Juan C.
, p. 2435 - 2448 (2007/10/03)
A wide variety of 1,6-enynes and 1,7-enynes incorporating γ-oxygenated-α,β-unsaturated phenylsulfone moieties have readily been prepared by piperidine-promoted condensation of the corresponding alkynyl aldehyde with phenylsulfonyl-(p-tolylsulfinyl)methane and further protection of the hydroxyl group. Despite the enduring claim concerning the unsuitability of electronically deficient olefins in Pauson - Khand reactions, we report that these 1-sulfonylated enynes are excellent substrates in intramolecular Pauson - Khand reactions under both thermal and amine N-oxide-promoted conditions. Moreover, in contrast with the usual exo-selective Pauson - Khand cyclization of allylic substituted enynes, the reactions of these 1-sulfonylated-3-oxygenated enynes occur with a moderate or high endo selectivity. The evaluation of the chemical and stereochemical scope of the process in comparison with the Pauson - Khand cyclization of non-sulfonylated enynes, its application to the stereo-selective preparation of optically pure C6-substituted bicyclo[3.3.0]oct-1-en-3-ones, and the interpretation of the stereochemical outcome are also discussed.
