172589-32-1Relevant articles and documents
Asymmetric catalysis of Diels-Alder cycloadditions by an MS-free binaphthol-titanium complex: Dramatic effect of MS, linear vs positive nonlinear relationship, and synthetic applications
Mikami, Koichi,Motoyama, Yukihiro,Terada, Masahiro
, p. 2812 - 2820 (2007/10/02)
Asymmetric Diets-Aider (D.-A.) reaction of 5-hydroxynaphthoquinone (juglone) with butadienyl acetate catalyzed by the binaphthol-derived chiral titanium (BINOL-Ti) complex 1 proceeds in only 9% ee in the presence of molecular sieves (MS). Remarkably, however, this reaction proceeds in 76-96% ee with BINOL-Ti complex 1 freed from MS to provide the endo-adducts useful for the synthesis of anthracyclines and tetracyclines. The solid MS-free BINOL-Ti complex 1 is stable for months at -20°C. Enhancements in endo selectivity and asymmetric induction are observed with the MS-free BINOL-Ti 1 also in the catalyzed D.-A. cycloaddition of methacrolein and glyoxylate with 1,3-dienol ethers and esters. The glyoxylate adducts can be converted to the mevinolin (compactin) intermediates. Surprisingly, the MS-free complex 1 exhibits not only a linear relationship between the ee's of BINOL-Ti 1 and the D.-A. products but also a positive nonlinear effect (asymmetric amplification), depending simply on the mixing manner of (R)-1 with (S)-1 or (±)-1.
Diels-Alder reactions: Rate acceleration promoted by a biphenylenediol
Kelly, T. Ross,Meghani, Premji,Ekkundi, Vadiraj S.
, p. 3381 - 3384 (2007/10/02)
The presence of biphenylenediol 8 accelerates the rate of some Diels-Alder reactions. Catalysis via a complex involving two hydrogen bonds (see 6) is proposed.
