1228992-58-2Relevant articles and documents
Modular mesoionics: Understanding and controlling regioselectivity in 1,3-dipolar cycloadditions of Muenchnone derivatives
Morin, Marie S. T.,St-Cyr, Daniel J.,Arndtsen, Bruce A.,Krenske, Elizabeth H.,Houk
, p. 17349 - 17358 (2014/01/06)
1,3-Dipolar cycloadditions of mesoionic 1,3-dipoles (Muenchnones, imino-Muenchnones, and phospha-Muenchnones) with alkynes offer versatile, modular synthetic routes to pyrroles. Reactivity and regioselectivity differ markedly for different members of this series, and we report here the first general rationale for differences in reactivity by means of a systematic investigation of 1,3-dipolar cycloadditions involving electron-poor and electron-rich alkynes. Competition kinetic measurements indicate that Muenchnones and phospha-Muenchnones are nucleophilic 1,3-dipoles that react most rapidly with electron-poor alkynes. However, the regioselectivities of cycloadditions are found to undergo an inversion as a function of alkyne ionization potential. The exact point at which this occurs is different for the two dipoles, allowing rational control of the pyrrole formed. The origins of these reactivities and regioselectivities are examined computationally. Frontier molecular orbital predictions are found not to be accurate for these reactions, but transition state calculations give correct predictions of reactivity and selectivity, the origins of which can be analyzed using the distortion/ interaction model of reactivity. Cycloadditions with electron-poor alkynes are shown to favor the regioisomer that has either the most favorable TS interaction energy (Muenchnones or imino-Muenchnones) or the smallest TS distortion energy (phospha-Muenchnones). Cycloadditions with more electron-rich aryl-substituted alkynes, on the other hand, generally favor the regioisomer that has the smaller TS distortion energy. These insights delineate the synthetically important distinctions between Muenchnones and phospha-Muenchnones: phospha-Muenchnones undergo highly regioselective cycloadditions with electron-poor alkynes that do not react selectively with Muenchnones, and the reverse is true for cycloadditions of Muenchnones with electron-rich alkynes.
Phospha-Muenchnones: Electronic structures and 1,3-dipolar cycloadditions
St-Cyr, Daniel J.,Morin, Marie S. T.,Belanger-Gariepy, Francine,Arndtsen, Bruce A.,Krenske, Elizabeth H.,Houk
scheme or table, p. 4261 - 4273 (2010/08/06)
The reaction of imines, acid chlorides, PR3, and base generates a new class of 1,3-dipoles: phospha-Muenchnones. These 1,3-dipoles can undergo cycloadditions with alkynes followed by loss of phosphine oxides to form pyrroles. Cycloaddition reac
