Photocatalyic Appel reaction enabled by copper-based complexes in continuous flow

Abstract

A copper-based photocatalyst, Cu(tmp)(BINAP)BF4, was found to be active in a photoredox Appel-type conversion of alcohols to bromides. The catalyst was identified from a screening of 50 complexes and promoted the transformation of primary and secondary alcohols to their corresponding bromides and carboxylic acids to their anhydrides. The protocol was also amendable and optimized under continuous flow conditions.

Phosphine Evaluation on a New Series of Heteroleptic Copper(I) Photocatalysts with dpa Ligand [Cu(dpa)(P,P)]BF4

“…NMR spectra were recorded on NMR Bruker AV 400 MHz and AV 300 MHz. Chemical shifts are given in parts per million relatives to TMS ( 1 H and 13 C, δ(SiMe 4 ) = 0). Most NMR assignments were supported by additional 2D experiments.…”

“…1 H-NMR (400 MHz, CDCl 3 , 298 K): δ/ppm = 9.0 (s,1H, NÀ H), 7.70 (dd, J = 5.7 Hz, 1.7 Hz, 2H), 7.50 (ddd, J = 8.9 Hz, 7.2 Hz, 1.9 Hz, 2H), 7.36 (d, J = 8.3 Hz, 2H), 7.34-7.26 (m, 6H), 7.23 (t, J = 7.5 Hz, 8H), 7.13 (dt, J = 7.1 Hz, 5.0 Hz, 8H), 7.06-6.98 (m, 4H), 6.91-6.85 (m, 2H), 6.48 (t, J = 6.4 Hz, 2H). 13 C{ 1 H} NMR (100 MHz, CDCl 3 , 298 K): δ/ppm = 157.8 (t, J C-P = 6.2 Hz), 153.8, 147.1, 138.7, 134.3, 133.2 (t, J C-P = 8.2 Hz), 131.7, 131.1 (t, J C-P = 16.0 Hz), 129.9, 128.7 (t, J C-P = 4.7 Hz), 125.0, 124.6 (t, J C-P = 13.1 Hz), 120.1, 116.8, 115.8. 19 F NMR (400 MHz, CDCl 3 , 298 K): δ/ppm = À 151.17 (s, BF 4 ), 11 B NMR (128 MHz, CDCl 3 , 298 K): δ/ppm = À 0.64 (s, BF 4 ).…”

Making Copper Photocatalysis Even More Robust and Economic: Photoredox Catalysis with [CuII(dmp)2Cl]Cl

“…Compound 8e: [10] Following general procedure (GP-A) using irradiation with green LED (λ max = 530 nm) for 30 h yielded 297.7 mg (402 μmol, 80 %) of 8e as a colorless oil after flash column purification (hexanes). Compound 10a: [9] Following general procedure (GP-A) using irradiation with blue LED (λ max = 455 nm) for 30 Compound 10b: [9] Following general procedure (GP-A) using irradiation with blue LED (λ max = 455 nm) for 30 h yielded 203.1 mg (458 μmol, 92 %) of 10b as a colorless oil after flash column purification (hexanes). Compound 10c: [9,36] Compound 10d: [9] Following general procedure (GP-D) using irradiation with blue LED (λ max = 455 nm) for 30 h yielded 21.7 mg (61 μmol, 12 %) of 10d as a white solid after flash column purification (hexanes/EtOAc, 9:1 to 4:1).…”

Heteroleptic Copper(I)-Based Complexes Incorporating BINAP and π-Extended Diimines: Synthesis, Catalysis and Biological Applications

“…Three mechanistically distinct photocatalytic transformations were pursued. In a visible-light Appel-type reaction (Figure 3) [28,29], the new BINAP-containing copper-based catalyst Cu(dpq)(BINAP)BF4 provided similar yields to other complexes having large-bite-angle bisphosphines. Note that control reactions performed in the absence of light or in the absence of catalyst at 450 nm did not afford any significant conversion to the alkyl bromide 2.…”