Synthesis of Naphthocyclobutenes from α-Naphthyl Acrylates by Visible-Light Energy-Transfer Catalysis

Abstract

Methyl (α-naphthyl) acrylates bearing an ortho-substituent with a hydrogen atom produce naphthocyclobutenes upon Ir(Fppy) 3 -mediated photosensitization. This reaction can be described as a carbon analogue of the Norrish−Yang reaction: upon triplet excitation of the acrylate a 1,5-HAT results in a 1,4-diradical which forms the cyclobutene. Diastereoselectivities up to >20:1 were observed for the ring-closure reaction.

Ligand-Free Copper(I)-Mediated Cross-Coupling Reactions of Organostannanes with Sulfur Electrophiles

“…The reaction mixture was stirred at 120 °C for 48 h and afforded after chromatographic purification on SiO2 (Hexanes/EtOAc, 30:1) 14g (14.8 mg, 58%) as a colorless oil: 1 H NMR (300 MHz, CDCl 3 ) δ 7.48–7.38 (m, 4H), 7.38–7.27 (m, 3H), 7.25–7.19 (m, 2H); 13 C­{ 1 H} NMR (75 MHz, CDCl 3 ) δ 143.0 ( J­( C–F) = 1.5), 133.7, 132.6, 129.8, 128.8, 128.4, 128.0, 143.0 ( J­( C–F) = 3.9), 122.4. Characterization data matched the literature report …”

“…The reaction mixture was stirred at 120 °C for 48 h and afforded after chromatographic purification on SiO2 (Hexanes/EtOAc, 30:1) 14g (14.8 mg, 58%) as a colorless oil: 1 Characterization data matched the literature report. 23 (4-Fluorophenyl)(phenyl)sulfane (14h). According to the general protocol A, tributylphenylstannane (55.1 mg, 0.150 mmol), 1,2-bis(4fluorophenyl)disulfane (25.4 mg, 0.100 mmol), KF (11.6 mg, 0.200 mmol), and CuCl (14.9 mg, 0.150 mmol) were added to anhydrous 1,4-dioxane (2.00 mL).…”

Visible‐Light‐Mediated Energy Transfer Enables the Synthesis of β‐Lactams via Intramolecular Hydrogen Atom Transfer

“…To the best of our knowledge, the first published report to make β‐lactam products feature in Sarpong and co‐worker's study, which is focused on keto‐amide cyclization under blue light irradiation [14f] . But, a notable variation using visible‐light by Koert and co‐workers must be highlighted (Scheme 1C) [15a] . Here they reported carbon‐to‐carbon 1,5‐HAT (rather than the typical carbon to oxygen 1,5‐HAT of the Norrish‐Yang cyclization) [15] through EnT mediated olefin triplet sensitization (rather than a triplet sensitized ketone) [16] .…”

Catalytic generation of ortho-quinone dimethides via donor/donor rhodium carbenes

“…Acetophenone 10 was the only observed product, which we presume emanates from enol ether 9 through a known process. 16,17 We next attempted to intercept the presumed o-QDM intermediate through a one-pot process and did not observe any Diels-Alder products. Finally, we prepared acetal 13, which would avoid enol ether formation.…”