Br-radical-mediated [3+2] annulation: synthesis of 2-bromomethylsubstituted alkenylcyclopentanes by the reaction of alkenylcyclopropanes with allyl bromides under photo irradiation Fukuyama, Takahide, Kippo, Takashi, Hamaoka, Kanako, Ryu, Ilhyong Sci. China Chem., 2019, 62, 11 pp. 1525 - 1528 DOI: 10.1007/s11426-019-9595-0
A radical chain addition of allyl bromides 2 to alkenylcyclopropanes 1 resulted in [3+2] annulation to give 2-bromomethyl-alkenylcyclopentanes 3 in good yields (16 examples). In this reaction, two kinetically fast radical reactions, cyclopropylcarbinyl radical-ring-opening and 5-exo-radical cyclization, preceded the β-fragmentation of a bromine radical to make the formal cycloaddition possible.
Radical Mediated Aza-Pauson-Khand Reaction of Acetylenes, Imines, and CO Leading to Five-Membered Unsaturated Lactams Fukuyama, Takahide, Okada, Takuma, Nakashima, Nao, Ryu, Ilhyong Helv. Chim. Acta, 2019, 102, 10 pp. - DOI: 10.1002/hlca.201900186
Formal [2+2+1] cycloaddition reaction involving acetylenes, aromatic imines, and CO was achieved by radical chain reaction, which gave five‐membered unsaturated lactams in modest to good yields. When we used 5‐chloropentyne, sequential carbonylation took place accompanied with double annulation events to give a cyclohexanone‐fused lactam in excellent stereoselectivity.
Revisiting Hydroxyalkylation of Phenols with Cyclic Carbonates Kao, Shih-Chieh , Lin, Yi-Ching , Ryu, Ilhyong, Wua, Yen-Ku Adv. Synth. Catal., 2019, 361, 15 pp. 3639 - 3644 DOI: 10.1002/adsc.201900287
Described is a tetrabutylammonium fluoride‐mediated hydroxyalkylation reaction of phenols with cyclic carbonates. This operationally simple method enables the synthesis of a variety of aryl β‐hydroxyethyl ethers in good to excellent yields with a very small amount of catalyst loading (0.1–1 mol%). Of particular note is the efficient conversion of aromatic diols and phloroglucinol to the corresponding bis‐ and tris‐hydroxyethylated products. To further showcase the versatility of this protocol, guaifenesin was prepared with a single step by the condensation of guaiacol and glycerol carbonate. We also developed a flow ethoxylation process permitting the continuous synthesis of multiflorol.
Synthesis of 4,4-Difluoroalkenes by Coupling of α‑Substituted α,αDifluoromethyl Halides with Allyl Sulfones under Photoredox Catalyzed Conditions Uno, Misae, Sumino, Shuhei, Fukuyama, Takahide, Matsuura, Makoto, Kuroki, Yoshichika, Kishikawa, Yosuke, Ryu, Ilhyong J. Org. Chem., 2019, 84, 14 pp. 9330 - 9338 DOI: 10.1021/acs.joc.9b00901
Photoredox-catalyzed allylation of α-gem-difluorinated organohalides with allyl sulfones proceeded smoothly under visible light irradiation to give 4,4-difluoroalkenes in good yields. In the presence of catalytic Ru(bpy)3Cl2, Hantzsch ester, and diisopropylethylamine, the reaction was complete within 2 h. Using the same methodology, three-component cascade reactions to give 6,6-difluoroalkenes were carried out successfully
The C(sp3)–H allylation of alkanes is investigated by using allyl bromides under radical reaction conditions. In many cases, methine C–H allylation preceded methylene and methyl C–H allylation with complete or a high degree of site selectivity. The C–H allylation of allylic compounds, such as allylbenzene, gives 1,5-dienes with the SH2′ reactions of the allyl radicals occurring at the less hindered carbon.
Kinetically Controlled Fischer Glycosidation under Flow Conditions: A New Method for Preparing Furanosides Masui, Seiji, Manabe, Yoshiyuki, Hirao, Kohtaro, Shimoyama, Atsushi, Fukuyama, Takahide, Ryu, Ilhyong, Fukase, Koichi Synlett , 2019, 30, 4 pp. 397 - 400 DOI: 10.1055/s-0037-1611643
Kinetically controlled Fischer glycosidation was achieved under flow conditions. β-Hydroxy-substituted sulfonic acid functionalized silica (HO-SAS) was used as an acid catalyst. This reaction directly converted aldohexoses into kinetically favored furanosides to enable the practical synthesis of furanosides. After optimization of the reaction temperature and residence time, glucofuranosides, galactofuranosides, and mannofuranosides were synthesized in good yields.
Carbonylation of Alkyl Radicals Derived from Organosilicates through Visible-Light Photoredox Catalysis Cartier, Alex, Levernier, Etienne, Corce, Vincent, Fukuyama, Takahide, Dhimane, Anne-Lise, Ollivier, Cyril, Ryu, Ilhyong, Fensterbank, Louis Angew. Chem. Int. Ed., 2019, 58, 6 pp. 1789 - 1793 DOI: 10.1002/anie.201811858
Primary, secondary, and tertiary alkyl radicals formed by the photocatalyzed oxidation of organosilicates underwent efficient carbonylation with carbon monoxide (CO) to give a variety of unsymmetrical ketones. This study introduces the possibility of radical carbonylation under a photooxidative regime.