Rhodium‐Catalyzed Arylation of Cyclopropenes Based on Asymmetric Direct Functionalization of Three‐Membered Carbocycles

Abstract

A variety of highly diastereo- and enantiomerically enriched arylcyclopropanes is obtained through the asymmetric rhodium-catalyzed arylation reaction of achiral nonfunctionalized cyclopropene derivatives with commercially available aryl boronic acids in the presence of (R,S)-Josiphos.

Cobalt‐Catalyzed Diastereo‐ and Enantioselective Hydroalkenylation of Cyclopropenes with Alkenylboronic Acids

“…[3a] To gain some preliminary insight into the reaction mechanism, as eries of experiments were conducted. In contrast to the Rh-catalyzed system, [28] the addition of 4.0 equivalents of either CD 3 OD or D 2 Oresulted in asignificant erosion of efficiency.Only 20 %D-labelled product was obtained, indicating that it is more likely that the boronic acid supplied the proton (Scheme 5a). Asingle diastereomer (3x) was obtained using the deuterium-labeled substrate 1d, indicating the addition of the alkenyl/Co complex to the cyclopropene occurred in a syn-fashion, and no racemerization of the resulting Co À Cb ond was observed during the protonation process (Scheme 5b).…”

“…Thea ssortment of enantioenriched multisubstituted cyclopropanes can be functionalized in an umber of ways to afford valuable and otherwise difficult-to-access building blocks (Scheme 4). In contrast to the Rh-catalyzed system, [28] the addition of 4.0 equivalents of either CD 3 OD or D 2 Oresulted in asignificant erosion of efficiency.Only 20 %D-labelled product was obtained, indicating that it is more likely that the boronic acid supplied the proton (Scheme 5a). and 70:30 d.r., respectively.…”

“…[25] Theonly pioneering work is the Cu-catalyzed protocol with alkenylaluminum reagents as nucleophiles,a lbeit in moderate efficiency and enantiose- lectivity,and with limited scope. [28] Herein, we disclosed the first Co-catalyzed enantioselective hydroalkenylation of cyclopropenes,u sing awide range of alkenylboronic acids,todeliver products with high diastereo-and enantioselectivities (Scheme 1c). Thec hallenge for such ap rocess is the lower reactivity compared with other organometallic reagents.E levated reaction temperatures might be required to enhance the efficiency.…”

“…Therefore,itisnontrivial to achieve high diastereo-and enantioselectivity.Abreakthrough on the first Rh-catalyzed enantioselective hydroarylation of 3,3disubstituted cyclopropenes was reported by Marek and coworkers in 2018. [28] Herein, we disclosed the first Co-catalyzed enantioselective hydroalkenylation of cyclopropenes,u sing awide range of alkenylboronic acids,todeliver products with high diastereo-and enantioselectivities (Scheme 1c). [29] We commenced our studies with the reaction of the 3,3disubstituted cyclopropene 1a with the alkenylboronic acid 2a in the presence of various phosphine/Co complexes (Table 1).…”

Rhodium‐Catalyzed Arylation of Cyclopropenes Based on Asymmetric Direct Functionalization of Three‐Membered Carbocycles

“…As we have ar ather broad scope for the introduction of aryl boronic acids possessing either electron-donating or electron-withdrawing substituents with good to excellent diastereo-and enantioselectivities,w ew ere interested in extending the scope of this reaction to various cyclopropene species (Scheme 3). Cyclopropenes containing as ubstituent on the aromatic group (2m-p)u ndergo the asymmetric arylation reaction with similar selectivities.T he absolute configuration of the cyclopropane product was determined by X-Ray crystallographic analysis of 2m (see the Supporting Information) [22] and assigned by analogy for all other products.W hent he solvent mixture was changed to toluene/1,4dioxane/D 2 O, the 1,2,3-polysubstituted cyclopropane 2n was obtained with a syn diastereoselectivity between the aryl group of the boronic acid and the deuterium, thus confirming the syn addition of the aryl rhodium species across the double bond of the three-membered ring. [23] When the substituents on the cyclopropane are fused in ac yclic structure,t he aryl addition proceeds with similar diastereo-and enantioselectivity (2q).…”