Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.
J Am Chem Soc. 2015 Mar 25;137(11):3767-70. doi: 10.1021/jacs.5b01036. Epub 2015 Mar 16.
Cu/nitroxyl catalysts have been identified that promote highly efficient and selective aerobic oxidative lactonization of diols under mild reaction conditions using ambient air as the oxidant. The chemo- and regioselectivity of the reaction may be tuned by changing the identity of the nitroxyl cocatalyst. A Cu/ABNO catalyst system (ABNO = 9-azabicyclo[3.3.1]nonan-N-oxyl) shows excellent reactivity with symmetrical diols and hindered unsymmetrical diols, whereas a Cu/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl) displays excellent chemo- and regioselectivity for the oxidation of less hindered unsymmetrical diols. These catalyst systems are compatible with all classes of alcohols (benzylic, allylic, aliphatic), mediate efficient lactonization of 1,4-, 1,5-, and some 1,6-diols, and tolerate diverse functional groups, including alkenes, heterocycles, and other heteroatom-containing groups.
已鉴定出铜/亚硝酰基催化剂，在温和的反应条件下，使用环境空气作为氧化剂，可促进二醇的高效和选择性有氧氧化内酯化。通过改变亚硝酰共催化剂的身份，可以调整反应的化学和区域选择性。Cu/ABNO 催化剂体系（ABNO = 9-氮杂双环[3.3.1]壬烷-N-氧自由基）与对称二醇和受阻不对称二醇具有极好的反应性，而 Cu/TEMPO 催化剂体系（TEMPO = 2,2,6,6-四甲基-1-哌啶基-N-氧自由基）对非对称二醇的氧化具有极好的化学和区域选择性。这些催化剂体系与所有醇类（苄基、烯丙基、脂肪族）相容，可有效内酯化 1,4-、1,5-和一些 1,6-二醇，并能耐受各种官能团，包括烯烃、杂环和其他含杂原子的基团。
