Catalytic regio- and stereoselective silicon–carbon bond formations on unsymmetric gem-difluorocyclopropenes by capture of silyl metal species

Abstract

We report herein that a highly regioselective silicon-carbon bond-forming silylation of unsymmetric gem-difluorocyclopropenes based on Si-C or Si-B bond cleavage of organosilicon reagents was achieved using palladium or copper catalysis...

Experimental and Theoretical Studies on Stereomutation Through gem‐Difluorocyclopropanylide Intermediates

“…In this study, we employed enantioenriched 3-phenyl-2,2difluoromethyl-3-silylcyclopropanes 1 which were prepared by the copper-catalyzed asymmetric hydrosilylation. [17,18] The 4substituted phenyl groups in 1 would be useful to discuss correlations between the electronic properties and the reduction of enantiopurity of the corresponding 2,2-difluorocyclopropanes 2. Table 1 summarizes the desilylation of 1 affording 2.…”

“…[15] Recently, copper-catalyzed asymmetric hydrosilylation of gem-difluorocyclopropenes has been investigated, and the corresponding enantioenriched silyl-substituted gem-difluorocyclopropanes have been furnished (Scheme 1). [17,18] Meanwhile, Xia and co-workers proposed rhodium-catalyzed stereoablative kinetic resolution of racemic gem-difluorocyclopropanes leading to the optically active compounds containing all-carbon quaternary stereocenters. [19] As an attempt at chemical conversions of the enantioenriched silyl-substituted gem-difluorocyclopropanes, we examined desilylation with tetrabutylammonium fluoride (TBAF).…”

Regio- and Diastereoselective Hydrophosphination and Hydroamidation of gem-Difluorocyclopropenes

“…In 2016 and 2021, Hu’s group successively reported the deoxyfluorinations of alcohols or carboxylic acids with gem -difluorocyclopropenes, in which the oxyanion of the alcohols or carboxylic acids selectively attacked the difluorine carbon atom of gem -difluorocyclopropenes (Scheme b) . The apparently different chemo- and regioselectivity between carbon (Group IV) and oxygen (Group VI)-based nucleophilic reagents in their reactions with gem -difluorocyclopropenes intrigued us. We wondered what would happen if Group V elements such as nitrogen and phosphorus were employed.…”

An unusualtrans-hydrosilylation of prochiral 1,1-disubstituted cyclopropenes revealing the different nature of asymmetric palladium and rhodium catalysis

“…This is likely due to low reactivity of internal alkenes for unproductive chelation with transition-metal catalysts, resulting in the need for special ligands to allow acceptable reaction rates and efficiency as well as stereoselective control. A limited number of previous examples of enantioselective transition-metal-catalyzed hydrosilylation of internal alkenes include Pt-catalyzed hydrosilylation of alkenyl boronates with PhMe 2 SiH, 13 Pd-catalyzed Si–C bond-forming transformations of HSiCl 3 or other monohydrosilanes with norbornene, 14 β-silyl styrene, 15 or maleimides, 16 Cu or Co-catalyzed desymmetric hydrosilylation of prochiral disubstituted cyclopropenes, 17 and Cu-catalyzed hydrosilylation of 1,2-dihydroquinolines with Ph 2 SiH 2 . 18 In this context, inspired by previous reports on transition-metal-catalyzed hydrometallation-initiated functionalizations of cyclopropenes (Fig.…”