2,5-Dimethoxy-2,5-dihydrofuran chemistry: a new approach to 2(5H)-furanone derivatives

Toward the Total Synthesis of Klaivanolide: Complete Reinterpretation of Its Originally Assigned Structure

“…These differences could be a result of the size of the ring, which distorts the ethylene moiety and changes the corresponding dihedral angle. Figure 1 shows the value of reported coupling constants for vicinal ethylene protons of α,β‐unsaturated lactones or cyclic ketones as a function of the ring size and emphasizes that the ring strain has a strong influence on this variable, because cyclobutenone,12 butenolide,13 pentenolide,14 hexenolide,15 and heptenolide16 exhibit vicinal coupling constants for ethylene protons of 2.3, 5.8, 9.5, 12.4 and 13.0 Hz, respectively. By comparing vicinal coupling constants of ethylene protons of compound 1 and isolated klaivanolide, 12.1 and 5.5 Hz, respectively, we could postulate that isolated klaivanolide contains a butenolide rather than a hexenolide.…”

Supported gold nanoparticles as a reusable catalyst for synthesis of lactones from diols using molecular oxygen as an oxidant under mild conditions

“…9 The obtained HT (1.0 g) was then added to 50 mL of an aqueous solution of HAuCl 4 (2 mM). Interestingly, adding Na 2 CO 3 as a base to the reaction mixture for the Au/TiO 2 system significantly improved the yield of 2 (entry 18 vs. 19). Subsequent treatment with KBH 4 at room temperature for 1 h yielded Au/HT as a purplish red powder.…”

Photoredox-Catalyzed Ring-Opening Addition Reaction between Benzyl Bromides and Cyclic Ethers

“…It was found that the addition of ZnBr 2 (as additive) promoted the yield, and the equivalents of THF (2a) have influence on the yield (entries [6][7][8][9]. The control experiments without either Ir(ppy) 3 catalyst or blue light irradiation demonstrated the necessity of the visible light promoted photoredox catalysis (entries 10,11). Although the addition of ZnBr 2 was beneficial for the yield of desired product 3a, it also brought about the side product 4a (entry 12).…”

“…We envisaged that both bromide ion (as a nucleophile) and carbocation (as an electrophile) could add to one molecule (like cyclic ethers), thus affording a new product with high atom economy (Scheme 1c). Indeed, the ring-opening reaction between alkyl bromides and cyclic ethers is rare, 9,10 although the reaction between acyl halides and cyclic ethers under Lewis acid catalysis has been systematically studied. 8 a Reaction conditions: unless otherwise mentioned, the mixture of 1a (0.2mmol), 2a, Ir(ppy)3 (1 mol%), additive, and solvent (2 mL) was stirred under the irradiation by blue LEDs at room temperature for 24 h.…”