Gold(I)-Catalyzed Ring Expansions of Unactivated Alkynylcyclopropanes to (<i>E</i>)-2-Alkylidenecyclobutanamines in the Presence of Sulfonamides
作者:Siyu Ye、Zhi-Xiang Yu
DOI:10.1021/ol9028786
日期:2010.2.19
The ringexpansion of cyclopropane derivatives provides a powerful method to construct synthetically useful four-membered carbocycles. Herein, a new type of gold(I)-catalyzed ringexpansion of an unactivated alkynylcyclopropane/sulfonamide trapping strategy to (E)-2-alkylidenecyclobutanamines was described. The reaction tolerates a range of aryl and alkyl substituents with moderate to good yields.
Ring-Opening Regio-, Diastereo-, and Enantioselective 1,3-Chlorochalcogenation of Cyclopropyl Carbaldehydes
作者:Jan Wallbaum、Lennart K. B. Garve、Peter G. Jones、Daniel B. Werz
DOI:10.1002/chem.201605265
日期:2016.12.23
sulfenyl and selenyl chlorides to afford 1,3‐chlorochalcogenated products. The transformation is achieved by a merged iminium–enamine activation. The enantioselective desymmetrization reaction, leading to three adjacent stereocenters, furnished the target products in complete regioselectivity and moderate to high diastereo‐ and enantioselectivities (d.r. up to 15:1 and e.r. up to 93:7).
Cyclopropyl Iminium Activation: Reactivity Umpolung in Enantioselective Organocatalytic Reaction Design
作者:Christof Sparr、Ryan Gilmour
DOI:10.1002/anie.201103360
日期:2011.8.29
concept of cyclopropyl iminium activation for the organocatalytic desymmetrization of meso‐cyclopropylcarbaldehydes is presented. A combination of nucleophilic and electrophilic chlorinating reagents leads to a formal addition of Cl2 across one of the cyclopropyl bonds giving access to 1,3‐dichlorides in an enantioselective, catalytic fashion.