Desymmetrisation of meso difuryl alcohols, diols and their derivatives: complementary directed and undirected asymmetric dihydroxylation reactions
作者:Robert Hodgson、Tahir Majid、Adam Nelson
DOI:10.1039/b204904j
日期:2002.7.11
Asymmetric reactions (for example, asymmetric epoxidation and asymmetric dihydroxylation) were examined for the desymmetrisation of the meso substrates 1,1-difuran-2-ylmethanol, N-(1,1-difuran-2-ylmethyl)-4-methylbenzenesulfonamide, (R,S)-1,4-difuran-2-ylbutane-1,4-diol and the derivatives of these compounds. The complex OsO4·(S,S)-1,2-diphenyl-N,N′-bis(2,4,6-trimethylbenzyl)ethane-1,2-diamine was found to be an effective reagent for the desymmetrisation of meso-1,2-bis(3,6-dihydro-3-hydroxy-2H-pyran-2-yl)ethanes and the corresponding di-p-methoxybenzoates by asymmetric dihydroxylation. The stereochemical outcome of this process depends critically on the relative stereochemistry and substitution of the substrate, and can occur anti to, or be directed by, an allylic alcohol or p-methoxybenzoyloxy functional group.
研究了 1,1-二呋喃-2-基甲醇、N-(1,1-二呋喃-2-基甲基)-4-甲基苯磺酰胺、(R,S)-1,4-二呋喃-2-基丁烷-1,4-二醇和这些化合物的衍生物的不对称反应(例如不对称环氧化反应和不对称二羟基化反应)。研究发现,OsO4-(S,S)-1,2-二苯基-N,N′-双(2,4,6-三甲基苄基)乙烷-1,2-二胺复合物是一种有效的试剂,可通过不对称二羟基化作用,使介-1,2-双(3,6-二氢-3-羟基-2H-吡喃-2-基)乙烷和相应的二对甲氧基苯甲酸酯发生去对称化反应。这一过程的立体化学结果主要取决于底物的相对立体化学性质和取代情况,并可能与烯丙基醇或对甲氧基苯甲酰氧基官能团发生反应或受其引导。