Copper(II)-Mediated Ring Opening/Alkynylation of Tertiary Cyclopropanols by Using Nonmodified Terminal Alkynes

Abstract

The copper­(II)-mediated ring opening/alkynylation of cyclopropanol by employing inexpensive and commercially available terminal alkyne is developed. The reactions proceeded efficiently to afford synthetically useful alk-4-yn-1-ones in moderate to good yields with good functional group tolerance. Control experiments showed that the reaction presumably proceeds via the formation of intermediates of copper homoenolate and/or alkynylcopper species.

Switchable Mono‐ and Dipropargylation of Amino Alcohols: A Unique Property of the Iodide Anion in Controlling Ring‐Opening Alkynylation

“…Compared to the iodide anion, the highly electronegative chloride anion resists the π‐coordination of the carbon‐carbon triple bond to the copper catalyst, [14] which may promote the deprotonation of alkyne 2 to form copper‐ 4‐ alkyne complex B . Finally, ring‐opening alkynylation [15] of the intermediate 4 is accomplished, delivering the target product 5 , unless iodine salt is present.…”

Asymmetric β-arylation of cyclopropanols enabled by photoredox and nickel dual catalysis

“…2 In the presence of transition metal (TM) catalysis or single electron transfer (SET) catalysis, they have been widely applied in the synthesis of β-functionalized ketones by involving intermediates of homoenolates or β-keto radicals generated via ring-opening pathways, albeit mostly in racemic forms (Scheme 1A). 3,4 Despite recent advances, 5 the development of catalytic asymmetric strategies to access various enantioenriched β-functionalized ketones through ring-opening of cyclopropanols has proven to be quite challenging yet highly desirable.…”

Remote C(sp3)–H activation: palladium-catalyzed intermolecular arylation and alkynylation with organolithiums and terminal alkynes

“…Quite on the contrary, the construction of C(sp)–C(sp 3 ) bonds between terminal alkynes and alkyl halides was not often studied. 16–19 Therefore, the integration of the Sonogashira reaction with the activation of a C(sp 3 )–H bond might offer an appealing procedure, albeit remaining an immense challenge. The cross-coupling between C(sp)–H and C(sp 3 )–H was achieved by Li, who used a copper catalyst with a stoichiometric amount of peroxide.…”