Selective C–H Allylic Oxygenation of Cycloalkenes and Terpenoids Photosensitized by [Cu(Xantphos)(neoc)]BF₄

Abstract

We present herein for the first time the use of the [Cu­(Xantphos)­(neoc)]­BF4 as a photocatalyst for the selective C–H allylic oxygenation of cycloalkenes into the corresponding allylic hydroperoxides or alcohols in the presence of molecular oxygen. The proposed methodology affords the products at good yields and has also been applied successfully to several bioactive terpenoids, such as geraniol, linalool, β-citronellol, and phytol. A mechanistic study involving also kinetic isotope effects (KIEs) supports the proposed singlet oxygen-mediated reaction. On the basis of the high chemoselectivity and yields and the fast and clean reaction processes observed, the present catalytic system, [Cu­(Xantphos)­(neoc)]­BF4, has also been applied to the synthesis, at a laboratory scale, of the cis-Rose oxide, a well-known perfumery ingredient used in rose and geranium perfumes.

Direct and Indirect Chemiluminescence: Reactions, Mechanisms and Challenges

“…Recently, our team has also explored the role of Cu + complexes in the photochemical production of 1 O 2 . We found and presented for the first time that [Cu(Xantphos)(neoc)]BF 4 can be used as an alternative and very efficient photosensitizer in 1 O 2 -mediated C-H allylic oxygenations [146].…”

Photophysical properties of homobimetallic Cu(i)–Cu(i) and heterobimetallic Cu(i)–Ag(i) complexes of 2-(6-bromo-2-pyridyl)-1H-imidazo[4,5-f][1,10]phenanthroline

“…Since the groundbreaking work of α-diimine-Cu( i )–phosphine complexes with the earth-abundant and environmentally benign metal copper was reported by McMillin's group in the late 1970s, 1,2 these systems have attracted more and more attention because of their good room temperature phosphorescence in the solid state, long luminescence lifetime and tunable emission, 3–35 followed by the corresponding applications in organic light-emitting diodes (OLEDs), 11,13,24–27 bioimaging, 28 chemosensors, 10,29–32 and photocatalysis. 14,18,33–35 In recent years, the thermally activated delayed fluorescence (TADF) exhibited by α-diimine-Cu( i )–phosphine complexes led to their further development into a research boom. 26,33–35 However, the relatively low emission efficiency in the solutions has become the main obstacle to their applications.…”

“…14,18,33–35 In recent years, the thermally activated delayed fluorescence (TADF) exhibited by α-diimine-Cu( i )–phosphine complexes led to their further development into a research boom. 26,33–35 However, the relatively low emission efficiency in the solutions has become the main obstacle to their applications. 3–38 To solve this problem, some strategies have been adopted.…”

“…26,33–35 However, the relatively low emission efficiency in the solutions has become the main obstacle to their applications. 3–38 To solve this problem, some strategies have been adopted. First, the light-harvesting ability of the system is improved by increasing the conjugation degree and rigidity of the α-diimine ligands.…”

The Pivotal Role of Chemistry in Research and Development

“…Chemistry also plays a central role in the discovery of new compounds, and the synthesis of natural products, drugs and other pharmaceutical products with significant scientific, societal and environmental impact [27,28].…”