Nondirected Copper-Catalyzed Sulfoxidations of Benzylic C–H Bonds
作者:Hao Yu、Zhen Li、Carsten Bolm
DOI:10.1021/acs.orglett.8b00615
日期:2018.4.6
A copper-catalyzed sulfoxidation of benzylic C–H bonds by nondirected oxidative C(sp3)-H activation was developed. The process proceeds via sulfenate anions, which are generated by base-triggered elimination of β-sulfinyl esters and benzyl radicals. The functional group tolerance is high, and the product yields are good.
We disclose a direct C(sp)–, C(sp2)–, and C(sp3)–H thiolation reaction using β-sulfinylesters as the versatile sulfur source. The key step of this protocol is chemoselective C–S bond cleavage of the sulfoniumsalts that are formed in situ from the corresponding alkenes, alkynes, and 1,3-dicarboxyl compounds with β-sulfinylesters. The successful capture of the acrylate byproduct supports a retro-Michael
Preliminary results concerning a conceptually novel route to chiral sulfoxides based on the asymmetric alkylation of sulfenate salts with alkyl halides mediated by a chiral phase-transfer catalyst are described. As a representative example, o-anisyl methyl sulfoxide was produced in 96% yield and with an enantiomeric excess of 58% using commercial cinchonidinium derivative 2a.
Metal-Free Electrophilic Alkynylation of Sulfenate Anions with Ethynylbenziodoxolone Reagents
作者:Stephanie G. E. Amos、Stefano Nicolai、Alec Gagnebin、Franck Le Vaillant、Jerome Waser
DOI:10.1021/acs.joc.9b00050
日期:2019.3.15
Alkynyl sulfoxides are important buildingblocks with a unique reactivity in organic chemistry, but only a few reliable methods have been reported to synthesize them. A novel route to access alkynyl sulfoxides is reported herein by using ethynyl benziodoxolone (EBX) reagents to trap sulfenate anions generated in situ, via a retro-Michael reaction. The reaction takes place under metal-free and mild
Nickel catalyzed asymmetric synthesis of dienyl sulfoxides were accomplished with up to 98 % ee from both racemic allenyl carbonates and β-sulfinyl esters employing cheap Ni(II) as precatalyst. Experimental and computational methods revealed an interesting associated outersphere mechanism which is uncommon in transition metal catalyzed asymmetric allylic nucleophilic substitution reactions.