A visible-light-mediated annulation of N-sulfonylallylamines and olefins is reported. Rapid access to highly functionalized chloromethylated pyrrolidines can be achieved using mild conditions for the generation of nitrogen-centered radicals. Both a transition-metal-based catalyst and an organic dye can be used as photosensitizers with 0.5 mol % loading. The reaction was found to be applicable to a large variety of electron-rich and electron-neutral olefins.
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http://dx.doi.org/10.1021/acs.joc.7b02146 | DOI Listing |
Angew Chem Int Ed Engl
November 2024
Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, Innovative Drug Research Center, School of Pharmaceutical Sciences, Chongqing University, Chongqing, 401331, P. R. China.
A facile photochemical, one-pot synthesis of highly functionalized 1-aminotetralins derivatives (>70 examples) from readily accessible o-alkyl and o-formyl aryl silylimines with olefins is described. A diradical-mediated hydrogen atom transfer (DHAT) of primary, secondary, and tertiary C(sp)-H bonds of o-alkyl arylsilylimines and C(sp)-H bonds of o-formyl arylsilylimines enabled a [4+2] annulation with olefins in excellent diastereoselectivity. This was accomplished upon irradiation at λ = 420 nm in the presence of thioxanthen-9-one (10 mol %) as the sensitizer via energy transfer.
View Article and Find Full Text PDFChem Commun (Camb)
September 2024
Department of Chemistry, Visva-Bharati (A Central University), Santiniketan, 731235, West Bengal, India.
A new visible-light-mediated non-directed oxidative annulation between 2-arylindazoles and electron-deficient olefins using commercially available piperidine-1-sulfonyl chloride as the radical precursor to afford fused 5,6-dihydroindazolo[2,3-]quinolines has been developed under mild reaction conditions. This transformation occurs two consecutive C-H bond functionalizations. The mechanistic investigation results indicate that the reaction progresses through a radical pathway forming a 2-(2-aryl-2-indazol-3-yl)-3-piperidin-1-ylsulfonyl derivative as an intermediate.
View Article and Find Full Text PDFMolecules
February 2024
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA.
We present the first example of visible-light-mediated multicomponent annulation of 1,7-diynes by taking advantage of quadruple cleavage olf carbon-halogen bonds of BrCCl to generate a C1 synthon, which was adeptly applied to the preparation of skeletally diverse 3-benzoyl-quinolin-2(1)-one acetates in moderate to good yields. Controlled experiments demonstrated that HO acted as both oxygen and hydrogen sources, and -dichlorovinyl carbonyl compound exhibited as a critical intermediate in this process. The mechanistic pathway involves Kharasch-type addition/6-exo-dig cyclization/1,5-(SN")-substitution/elimination/binucleophilic 1,6-addition/proton transfer/tautomerization sequence.
View Article and Find Full Text PDFJ Org Chem
December 2023
College of Chemistry and Chemical Engineering, Yangtze Normal University, Chongqing 408000, China.
J Org Chem
February 2023
Department of Chemistry, Indian Institute of Technology Jodhpur, Karwar, Rajasthan 342037, India.
We conceptualized a novel disconnection approach for the synthesis of fused tetrahydroquinolines that exploits a visible light-mediated radical (4 + 2) annulation between alkyl -(acyloxy)phthalimides and -substituted maleimides in the presence of DIPEA as an additive. The reaction proceeds through the formation of a photoactivated electron donor-acceptor complex between alkyl NHPI esters and DIPEA, and the final tetrahydroquinolines were obtained in a complete regioselective fashion. The methodology features a broad scope and good functional group tolerance and operates under metal- and catalyst-free reaction conditions.
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