871949-71-2Relevant academic research and scientific papers
Cobalt porphyrin catalyzed [3+2] cycloaddition of cyclopropanes and carbonyl compounds
Shiba, Takahiro,Kuroda, Daiki,Kurahashi, Takuya,Matsubara, Seijiro
, p. 2005 - 2008 (2014)
A cobalt porphyrin efficiently catalyzed the formal [3+2] cycloaddition of alkyl-/aryl-substituted cyclopropanes and carbonyl compounds such as aldehydes and ketones to afford the corresponding substituted tetrahydrofurans. The use of the cobalt porphyrin complex as a Lewis acid to catalyze the reaction via the electrophilic activation of cyclopropanes was demonstrated. The high functional-group tolerance and robustness of the catalyst were also demonstrated. Further, the potential utility of the catalyst was demonstrated by performing the cycloaddition of cyclic ketones and cyclopropanes to afford spiro tetrahydrofurans. Georg Thieme Verlag Stuttgart · New York.
Scope and mechanism for Lewis acid-catalyzed cycloadditions of aldehydes and donor-acceptor cyclopropanes: Evidence for a stereospecific intimate ion pair pathway
Pohlhaus, Patrick D.,Sanders, Shanina D.,Parsons, Andrew T.,Li, Wei,Johnson, Jeffrey S.
, p. 8642 - 8650 (2008/12/23)
In this work, the one-step diastereoselective synthesis of cis-2,5-disubstituted tetrahydrofurans via Lewis acid catalyzed [3 + 2] cycloadditions of donor-acceptor (D-A) cyclopropanes and aldehydes is described. The scope and limitations with respect to both reaction partners are provided. A detailed examination of the mechanism has been performed, including stereochemical analysis and electronic profiling of both reactants. Experimental evidence supports an unusual stereospecific intimate ion pair mechanism wherein the aldehyde functions as a nucleophile and malonate acts as the nucleofuge. The reaction proceeds with inversion at the cyclopropane donor site and allows absolute stereochemical information to be transferred to the products with high fidelity. The mechanism facilitates the stereospecific synthesis of a range of optically active tetrahydrofuran derivatives from enantioenriched D-A cyclopropanes.
