Catalyst-controlled and visible light-induced acylmethylation and bromoacylmethylation of Morita–Baylis–Hillman acetates with α-bromo ketones: access to highly functionalized 1,5-dicarbonyl compounds

Abstract

Photoinduced acylmethyl radical procedures for the efficent and simple preparation of highly functionalized 1,5-dicarbonyl compounds from Morita-Baylis-Hillman acetates with a-bromo ketones are developed. The acylmethylation is carried out with rose...

Photoinduced Alkylsulfonylation and Cyanoalkylsulfonylation of Morita–Baylis–Hillman Adducts via Multicomponent Insertion of Sulfur Dioxide

“…According to experimental results and literature investigation, the present plausible routes for the assembly of allylic alkylsulfones 3 was proposed in Scheme 7a. 21 Initially, the photocatalyst Mes-Acr + ClO 4 − (PC) rapidly transformed into the excited state of PC* under visible light irradiation, which was reduced by potassium alkyltrifuoroborate 2 to produce alkyl radical and the reduced state photocatalyst (PC 12,15,22 TMEDA was oxidized by the excited state PC* to afford PC •− and TMEDA •+ . Cycloketone oxime ester 4a would take place a SET with PC •− to provide iminyl radical D and regenerate PC for the next catalytic cycle.…”

“…Subsequently, single-electron reduction between radical intermediate B and the PC •− gives anionic intermediate C, simultaneously regenerating the PC. The products 3 were formed by elimination of OAc anion from intermediate C. In the preparation of products 5 (Scheme 7b), 12,15,22 TMEDA was oxidized by the excited state PC* to afford PC •− and TMEDA •+ . Cycloketone oxime ester 4a would take place a SET with PC •− to provide iminyl radical D and regenerate PC for the next catalytic cycle.…”

“…The products 3 were formed by elimination of OAc anion from intermediate C . In the preparation of products 5 (Scheme b), ,, TMEDA was oxidized by the excited state PC* to afford PC •– and TMEDA •+ . Cycloketone oxime ester 4a would take place a SET with PC •– to provide iminyl radical D and regenerate PC for the next catalytic cycle.…”

“…Significantly, MBH adducts can be served as an excellent radical acceptor in organic synthesis since their distinctive structures incorporate an activated CC bond connected to electron-withdrawing groups. A great deal of radical donors, such as Langlois’ reagent, N -hydroxyphthalimide esters (NHPI esters), potassium organotrifluoroborates, tertiary amines, ethers, α-bromo ketones, or NHC-boranes have been proved to be ideal C or B-radical precursors under photoredox catalysis or electrocatalysis to provide numerous trisubstituted olefins (Scheme a). In addition, the aryl sulfonylation of MBH adducts has been identified as an efficient method to obtain allylic sulfones by exploiting various sulfonyl reactants .…”