Photoinduced Electron‐Transfer Processes of Phthalimides

Abstract

For Abstract see ChemInform Abstract in Full Text.

Photocyclization of Tetra- and Pentapeptides Containing Adamantylphthalimide and Phenylalanines: Reaction Efficiency and Diastereoselectivity

“…Selective excitation of the phthalimide moiety in peptides was accomplished by use of lamps with a maximal output at 300 nm, where the phthalimide absorbs light, and Phe, Phe­(OMe), or Phe­(OMe) 2 do not absorb light (for the absorption spectra see Figures S1 and S2 in the SI). The irradiations were performed in CH 3 CN–H 2 O in the presence of K 2 CO 3 as a base which is required to deprotonate the carboxylic acid at the C-terminus, namely, phthalimide derivatives in the triplet excited state react in photoinduced SET with reducing agents that have the donor oxidation potential < 1.6 V vs SCE . Since carboxylates are better reducing agents than carboxylic acids, − deprotonation is required for the SET to occur.…”

“…The irradiations were performed in CH 3 CN−H 2 O in the presence of K 2 CO 3 as a base which is required to deprotonate the carboxylic acid at the C-terminus, namely, phthalimide derivatives in the triplet excited state react in photoinduced SET with reducing agents that have the donor oxidation potential < 1.6 V vs SCE. 27 Since carboxylates are better reducing agents than carboxylic acids, 28−30 deprotonation is required for the SET to occur. Irradiations were also conducted in acetone−H 2 O in the presence of K 2 CO 3 where upon irradiation at 300 nm acetone is excited and acts as a triplet sensitizer.…”

“…Prepared according to the general procedure for the Boc deprotection from 9 (250 mg, 0.53 mmol) in 95% yield; 244 mg (95%); colorless solid; mp 202−204 °C; L-TFA×H-Phe [3, 2 ]-OBn (25). Prepared according to the general procedure for the Boc deprotection from 24 (1.63 g, 3.95 mmol) in 80% yield; 1.36 g (80%); yellow solid; mp 130−132 °C; TFA×H-Phe-Phe-OBn (27). Prepared according to the general procedure for the Boc deprotection from 26 (1.60 g, 3.18 mmol) in 72% yield; 1.19 g (72%); colorless solid, mp 154 °C; 1 TFA×H-Phe-Phe-Phe-OBn (29).…”

Photocatalytic α‐Oxyamination of Stable Enolates, Silyl Enol Ethers, and 2‐Oxoalkane Phosphonic Esters

“…The benefits of flow photochemistry have been discussed through many examples in the literature. [33][34][35][36][37] Compared to the batch reaction, the reaction in a glass capillary offers a larger irradiation surface. By using Equation (1) for the penetration depth l of light, a layer of l = 1.0 mm depth contributes to the photoreaction for ε = 2.1 ϫ 10 3 m -1 cm -1 and c = 2.0 ϫ 10 -3 m in which ε is the molar extinction coefficient and c the concentration of the chromophore [Ru(bpy) 3 ] 2+ .…”

Photoinduced Addition of Phthalimide to Unactivated Alkynes†

“…Intramolecular photo‐cyclization (2), intermolecular photocycloaddition (3) and photo‐addition (4–6) are the major processes that have been observed so far. Most of these reactions are initiated by single electron transfer (SET) from a donor to the excited phthalimide acceptor (7, 8). The intermolecular photochemistry of phthalimide (PHT‐H) has been much less extensively investigated.…”