1236313-44-2Relevant academic research and scientific papers
Formal [2 + 2 + 2] cycloaddition strategy based on an intramolecular propargylic ene reaction/diels-alder cycloaddition cascade
Robinson, Julia M.,Sakai, Takeo,Okano, Katsuhiko,Kitawaki, Takafumi,Danheiser, Rick L.
supporting information; experimental part, p. 11039 - 11041 (2010/09/17)
A formal, metal-free, [2 + 2 + 2] cycloaddition strategy is described based on a cascade of two pericyclic processes. The first step involves an intramolecular propargylic ene reaction of a 1,6-diyne to generate a vinylallene, which then reacts in an inter- or intramolecular Diels-Alder reaction with an alkenyl or alkynyl dienophile. Reactions involving unsymmetrical alkenyl and alkynyl dienophiles proceed with good to excellent regioselectivity, and the diastereoselectivity in the Diels-Alder step is also high, with endo cycloadducts produced as the exclusive products of the reaction. In the case of alkynyl dienophiles, [4 + 2] cycloaddition initially generates an isotoluene-type intermediate that isomerizes to the isolated aromatic product upon exposure to a catalytic amount of DBU at room temperature. The mechanism of several earlier fully intramolecular related transformations have been shown to involve an analogous process rather than the diradical-mediated pathways proposed previously.
