Diazotrifluoroethyl Radical: A CF₃-Containing Building Block in [3 + 2] Cycloaddition

Abstract

We present herein a visible-light-induced [3 + 2] cycloaddition of a hypervalent iodine­(III) reagent with α-ketoacids for the construction of 5-CF3-1,3,4-oxadiazoles that are of importance in medicinal chemistry. The reaction proceeds smoothly without a photocatalyst, metal, or additive under mild conditions. Different from the well-established trifluorodiazoethane (CF3CHN2), the diazotrifluoroethyl radical [CF3C­(·)­N2], a trifluoroethylcarbyne (CF3CĊ:) equivalent and an unusual CF3-containing building block, is involved in the present reaction system.

Visible Light-Induced Coupling Cyclization Reaction of α-Diazosulfonium Triflates with α-Oxocarboxylic Acids or Alkynes

“…These results indicate that DCM or CD 3 CN act as the hydrogen atom source to provide hydrogen radical for the formation of intermediate H from intermediate G (Scheme 3). On the basis of the mechanistic investigations and related literatures, [5][6][7][8][9][10][11]16 a plausible reaction mechanism for the formation of compounds 3 and 5 is proposed in Scheme 3. Initially, diazomethyl radical A and cation radical B are generated from α-diazosulfonium triflates 1 under the irradiation of blue light via homolytic S−C bond cleavage.…”

“…The 1 H NMR data are consistent with the reported values. 24 2-(4-Bromophenyl)-2-oxoacetic acid (2m 9 2-(3-Fluorophenyl)-2-oxoacetic acid (2p). 1 H NMR (500 MHz, CDCl 3 ): δ 8.05 (d, J = 7.7 Hz, 1H), 7.92 (d, J = 9.1 Hz, 1H), 7.50 (td, J = 8.0, 5.4 Hz, 1H), 7.36 (td, J = 8.3, 2.6 Hz, 1H), 5.49 (s, 1H).…”

“…The 1 H NMR data are consistent with the reported values. 9 2-Oxo-2-(o-tolyl)acetic acid (2r). 1 H NMR (500 MHz, CDCl 3 ): δ 8.07 (d, J = 7.7 Hz, 1H), 7.53 (t, J = 7.4 Hz, 1H), 7.39−7.31 (m, 2H), 5.76 (s, 1H), 2.59 (s, 3H).…”

Synthesis of [1,2,3]Triazolo-[1,5-a]quinoxalin-4(5H)-ones through Photoredox-Catalyzed [3 + 2] Cyclization Reactions with Hypervalent Iodine(III) Reagents

“…In 1998, the Livi group developed a 1,3-dipolar cycloaddition reaction with 2-nitro-phenyl azides and diethyl oxaloacetate sodium salt in anhydrous ethanol for the synthesis of [1,2,3]­triazolo­[1,5- a ]­quinoxalin-4­(5 H )-ones in three steps . In this context, a new interesting approach was reported in the literature by Cai and Ding et al, which involved a copper-catalyzed tandem reaction of 1-(2-haloaryl)­propiolamides with sodium azide through a [3 + 2] azide alkyne cycloaddition . Some drawbacks of the reported methods are ineluctable, such as requiring multiple reaction steps, with low efficiency, and a limited substrate scope.…”

Formal [4+1] cyclization of (thio/imido)hydrazides and ethyl 3,3,3-trifluoropropanoate: unified synthesis of 1,3,4-oxadiazoles, 1,3,4-thiadiazoles and 1,2,4-triazoles

“…Recently, the formal [4+1] annulation of hydrazides and a suitable C1 synthon has emerged as an appealing alternative approach to mono- or di-substituted 1,3,4-oxadiazoles due to its obvious straightforwardness. 3 Additionally, a multicomponent Ugi-type reaction of N -carbamoyl imines 4 as well as photoinduced decarboxylative cyclization with hypervalent iodine reagents 5 also provides intriguing choices for the synthesis of 1,3,4-oxadiazoles with special substituent patterns.…”