π-Facial Stereoselectivity in Diels−Alder Cycloadditions to 1-Oxaspiro[4.5]deca-6,9-dien-8-one. The Strong Directive Effect of Ether Oxygen in a Cross-Conjugated Ketone Setting
作者:Leo A. Paquette、Brandon B. Shetuni、Judith C. Gallucci
DOI:10.1021/ol0347895
日期:2003.7.1
[GRAPHICS]The title compound 1, prepared from 1,4-cyclohexanedione monoethylene ketal, was treated with several reactive dienes, including diphenylisobenzofuran and 9,10-dihydro-11,12-dimethylene-9,10-ethanoanthracene. These [4 + 2] cycloadditions proceed with a strong kinetic bias for bonding to the dienophile from the direction syn to the tetrahydrofuranyl oxygen and consequently hold value in stereoselective synthesis.
Stereoselectivity Control by Oxaspiro Rings during Diels−Alder Cycloadditions to Cross-Conjugated Cyclohexadienones: The <i>Syn</i> Oxygen Phenomenon
作者:Katsuo Ohkata、Yukiko Tamura、Brandon B. Shetuni、Ryukichi Takagi、Wataru Miyanaga、Satoshi Kojima、Leo A. Paquette
DOI:10.1021/ja047027t
日期:2004.12.1
parameters were determined for the cycloaddition of 1a and 2a to cyclopentadiene. The rate acceleration profile of solvents was in the order CF(3)CH(2)OH >> CH(3)CN approximately CH(2)Cl(2) for the production of 9a from 1a and CF(3)CH(2)OH >> CH(2)Cl(2) > CH(3)CN for the production of 21a from 2a, respectively. This spread in polarity had no major impact on product distribution, a phenomenon also reflected