Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390 USA.
Beilstein J Org Chem. 2011;7:570-7. doi: 10.3762/bjoc.7.66. Epub 2011 May 4.
A highly efficient synthesis of oxygenated 5,5-spiroketals was performed towards the synthesis of the cephalosporolides. Gold(I) chloride in methanol induced the cycloisomerization of a protected alkyne triol with concomitant deprotection to give a strategically hydroxylated 5,5-spiroketal, despite the potential for regiochemical complications and elimination to furan. Other late transition metal Lewis acids were less effective. The use of methanol as solvent helped suppress the formation of the undesired furan by-product. This study provides yet another example of the advantages of gold catalysis in the activation of alkyne π-systems.
我们成功实现了含氧 5,5-螺缩酮的高效合成，这是合成头孢洛利德的关键步骤。尽管存在区域化学复杂和消除生成呋喃的可能性，甲醇中的金（I）氯化物仍能诱导保护炔三醇的环异构化反应，同时进行脱保护反应，得到具有战略意义的羟化 5,5-螺缩酮。其他晚期过渡金属路易斯酸的效果则较差。使用甲醇作为溶剂有助于抑制不想要的呋喃副产物的形成。该研究为金催化在炔烃π-体系的活化中的优势提供了另一个例证。
