296795-18-1Relevant academic research and scientific papers
Functionalized BINOL derivatives as ligands for enantioselectively catalyzed aldol additions: Highly enantioselective synthesis of chiral β-hydroxy thioesters
Zimmer, Reinhold,Schefzig, Luise,Peritz, Anke,Dekaris, Vjekoslav,Reissig, Hans-Ulrich
, p. 1439 - 1445 (2004)
A series of 3,3′-disubstituted and 6,6′-disubstituted BINOL derivatives was synthesized and examined in typical titanium(IV) promoted aldol reactions. The model reaction of S-ketene silyl acetal 13 and aldehydes 12a and 12b revealed that 6,6′-dibromo-BINOL derivative (R)-6 is the ligand of choice for these transformations. Up to 97% yield with excellent enantioselectivity (ee > 97%) could be achieved. Scope and limitations were demonstrated using a series of aldehydes as substrates, which were generally transformed into their aldol adducts by the (R)-6/Ti(Oi-Pr)4 catalyst with good efficacy and high enantioselectivity.
Optimisation, scope and limitations of enantioselective aldol reactions of an S-ketene silyl acetal with aliphatic aldehydes under (R)-BINOL-titanium(IV) catalysis conditions
Zimmer, Reinhold,Peritz, Anke,Czerwonka, Regina,Schefzig, Luise,Reissig, Hans-Ulrich
, p. 3419 - 3428 (2007/10/03)
The Mukaiyama aldol reaction between the functionalised aldehydes 5 and the S-ketene silyl acetal 2 catalysed by 1,1'-binaphthyl-derived chiral titanium(IV) complex 4 afforded the corresponding aldol products 6 in good yields and with good to excellent enantioselectivities. The chemical yield could further be enhanced, without loss of stereoselection, by addition of phenol and/or molecular sieves. The presented aldol reactions with aluminium, boron and ytterbium-BINOL catalysts demonstrate that only low chiral induction can be achieved. Aldol product 6a was converted into an α-lipoic acid precursor 8, thus providing a formal synthesis of this biologically active compound. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
Application of complex aldol reactions to the total synthesis of phorboxazole B
Evans,Fitch,Smith,Cee
, p. 10033 - 10046 (2007/10/03)
The synthesis of phorboxazole B has been accomplished in 27 linear steps and an overall yield of 12.6%. The absolute stereochemistry of the C4-C12, C33-C38, and C13-C19 fragments was established utilizing catalytic asymmetric aldol methodology, while the absolute stereochemistry of the C20-C32 fragment was derived from an auxiliary-based asymmetric aldol reaction. All remaining chirality was incorporated through internal asymmetric induction, with the exception of the C43 stereocenter which was derived from (R)-trityl glycidol. Key fragment couplings include a stereoselective double stereodifferentiating aldol reaction, a metalated oxazole alkylation, an oxazole-stabilized Wittig olefination, and a chelation-controlled addition of the fully elaborated alkenyl metal side chain.
