Aryl Carbamates: Mechanisms of Orthosodiations and Snieckus–Fries Rearrangements
作者:Yun Ma、Ryan A. Woltornist、Russell F. Algera、David B. Collum
DOI:10.1021/acs.joc.9b00968
日期:2019.7.19
Aryl carbamates are orthometalated by sodium diisopropylamide (NaDA) in tetrahydrofuran. The resulting arylsodiums undergo Snieckus-Fries rearrangement to give orthoacylated phenols in good yield. The intermediate arylsodiums and resulting orthoacylated phenolates are suggested to be monomeric. The rate-limiting step in the two-step sequence depends on the steric demands of the carbamoyl moiety and
作者:Lekha Gupta、Alexander C. Hoepker、Kanwal J. Singh、David B. Collum
DOI:10.1021/jo802713y
日期:2009.3.6
Ortholithiations of a range of arenes mediated by lithium dilsopropylamide (LDA) in THF at -78 degrees C reveal substantial accelerations by as little as 0.5 mol % of LiCl (relative to LDA). Substrate dependencies suggest a specific range of reactivity within which the LiCl catalysis is optimal. Standard protocols with unpurified commercial samples of n-butyllithium to prepare LDA or commercially available LDA show marked batch-dependent rates-up to 100-fold-that could prove significant to the unwary practitioner. Other lithium salts elicit more modest accelerations. The mechanism is not discussed.
Singh, Kanwal J.; Hoepker, Alexander C.; Collum, David B., Journal of the American Chemical Society, 2008, vol. 130, p. 18008 - 18017
作者:Singh, Kanwal J.、Hoepker, Alexander C.、Collum, David B.