Synergistic Catalysis for the Umpolung Trifluoromethylthiolation of Tertiary Ethers

Abstract

The first transition-metal-free,s ite-specific umpolung trifluoromethylthiolation of tertiary alkylethers has been developed, achieving the challenging tertiary C(sp 3 )-SCF 3 coupling under redox-neutral conditions.T he synergism of organophotocatalyst 4CzIPN and BINOL-based phosphorothiols can site-selectively cleave tertiary sp 3 C(sp 3 )-O ether bonds in complex molecules initiated by ap olarity-matching hydrogen-atom-transfer (HAT) event. The incorporation of several competing benzylic and methine C(sp 3 )ÀHb onds in alkylethers has little influence on the regioselectivity.Selective difluoromethylthiolation of CÀOb onds has also been achieved. This represents not only an important step forward in trifluoromethylthiolation but also ap romising means for siteselective C À Ob ond functionalization of unsymmetrical tertiary alkyl ethers.

Photocatalytic C(sp3) radical generationviaC–H, C–C, and C–X bond cleavage

“…Unlike the SET-based strategies used above, Xie et al used dialkyl acetals as masked alcohols and conceived an HAT-enabled C–O trifluoromethylation reaction under a dual-photocatalytic manifold (Scheme 38). 159 Mechanistically, the thiophosphate co-catalyst was firstly oxidised by the excited 4-CzIPN to form a thiyl radical, which performed a highly regioselective HAT at the acetal α-C–H position. The ensuing dialkoxy radical underwent β-C–O cleavage and turned into an R˙.…”

Synthesis of Quaternary Carbon-Centered Benzoindolizidinones via Novel Photoredox-Catalyzed Alkene Aminoarylation: Facile Access to Tylophorine and Analogues

“…[13][14][15][16][17][18] To further understand the reaction mechanism in the absence of NBu 4 OP(O)(OBu) 2 , we performed some additional control experiments. First, we envisioned that the oxidation of the 50 was unlikely to be operative according to the redox potentials. Indeed, under the irradiation of blue light, photocatalyst A and PhtSCF 3 did not react (Scheme 2d), which is in accordance with the Stern-Volmer fluorescence-quenching experiments performed by Glorius group (no reaction between photocatalyst B and PhtSCF 3 occurred under irradiation).…”

Visible-Light-Promoted Desulfurative Alkylation of Alkyl Thianthrenium Salts with Activated Olefins

“…However, the high bond energy and high redox potential of the C−O bond in an alcohol 8 have limited its synthetic application in the field of photochemistry. To overcome these problems, redox derivatives prepared from alcohols, such as oxalates, 9 xanthates, 10 carboxylates, 11 and ethers, 12 have emerged in C−O bond cleavage under visible-light irradiation conditions. Notably, these methods are limited to secondary and tertiary alcohols.…”