The Ryu Research Group, Department of Chemistry, Graduate School of Science, Osaka Prefecture University

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Published in 2003

Broad-spectrum radical cyclizations boosted by polarity matching. Carbonylative access to α-stannylmethylene lactams from azaenynes and CO
Ryu, I., Miyazato, H., Kuriyama, H., Matsu, K., Tojino, M., Fukuyama, T., Minakata, S., Komatsu, M.
J. Am. Chem. Soc., 2003, 125, 19 pp. 5632 - 5633
DOI: 10.1021/ja034896u

Free-radical mediated stannylcarbonylation of azaenynes provides a general [n + 1]-type annulation approach leading to α-stannylmethylene lactams. The cyclization is unusual in its breadth, covering 4-exo, 5-exo, 6-exo, 7-exo, and 8-exo modes.

Cyclizative radical carbonylations of azaenynes by TTMSS and hexanethiol leading to α-silyl- and thiomethylene lactams. Insights into the E/Z stereoselectivities
Tojino, M., Ohtsuka, N., Fukuyama, T., Matsubara, H., Schiesser, C. H., Kuriyama, H., Miyazato, H., Minakata, S., Komatsu, M., Ryu, I.
Org. Biomol. Chem., 2003, 1, pp. 4262 - 4267
DOI: 10.1039/b309944j

Free-radical mediated cyclizative carbonylations of azaenynes were carried out using TTMSS as a radical mediator to compare the efficiency and the stereochemistry with those using tributyltin hydride. Using a substrate concentration of 0.1 M, the reactions gave good yields of α-silylmethylene lactams having four to seven-membered rings. The observed E-diastereoselectivity of the resulting vinylsilane moiety is in sharp contrast to the Z-selectivity observed during the analogous carbonylation using tributyltin hydride. When hexanethiol was used as the radical mediator, α-thiomethylene lactams were formed with E-favoring stereoselectivity again. Ab initio and DFT molecular orbital calculations on the stability of E and Z products were carried out for a set of five-membered methylene lactams bearing SnH3, SiH3, and SMe groups. The distinct thermodynamic preference for the Z-isomer was only predicted for the Sn-bearing lactam. A steric effect due to the bulky (TMS)3Si group is proposed for the E-selectivity observed in the TTMSS-mediated reaction.

Two types of intramolecular homolytic substitution reactions at group XIV atoms: unusual radical 1,4-Sn shifts from Si to C and carbonylative SHi reaction at Si
Studer, A., Amrein, S., Matsubara, H., Schiesser, C. H., Doi, T., Kawamura, T., Fukuyama, T., Ryu, I.
Chem. Commun., 2003, , pp. 1190 - 1191
DOI: 10.1039/b301755a

4-[(Trimethylstannyl)diphenylsilyl]butanoyl radical, arising from the corresponding 3-(stannylsilyl)propyl radical and CO, undergoes an SHi reaction at Si with extrusion of trimethyltin radical to give silacyclopentanone. The parent 3-(stannylsilyl)propyl radical was also found to isomerize to (3-stannylpropyl)silyl radical via a 1,4-Sn shift from Si to C with a rate constant of 9.3 × 104 s–1 at 80 °C. Ab initio and DFT MO calculations support a front-side attack mechanism.

Fluorous solvent as a new phase-screen medium between reagents and reactants in the bromination and chlorination of alcohols
Nakamura, H., Usui, T., Kuroda, H., Ryu, I., Matsubara, H., Yasuda, S., Curran, D. P.
Org. Lett., 2003, 5, 8 pp. 1167 - 1169
DOI: 10.1021/ol034060w

A perfluorohexane layer regulates the rate of reagent transport in the bromination and chlorination of alcohols. A fluorous triphasic U-tube method is effective for lighter reagents; the thionyl chloride layer (yellow) vanishes, and the chlorides are obtained from the right top organic layer in the chlorination of alcohols.

Phase-vanishing method: Friedel-Crafts acylation of thiophene with tin tetrachloride and its application to convenient parallel synthesis
Matsubara, H., Yasuda, S., Ryu, I.
Synlett., 2003, 2, pp. 247 - 249
DOI: 10.1055/s-2003-36806

Phase-vanishing (PV) method was applied to Friedel-Crafts acylations of aromatic compounds with tin tetrachloride as a Lewis acid. The reaction proceeded smoothly and acylation products were obtained in good yield. Parallel, four different Friedel-Crafts acylation reactions were carried out successfully based on the present PV method.



Laboratory for Advanced Organic Synthesis
Organization for Research Promotion Osaka Prefecture University
Sakai, Osaka 599-8531, JAPAN
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