Enantioselective cyanation/brook rearrangement/C-acylation reactions of acylsilanes catalyzed by chiral metal alkoxides
New catalytic enantioselective cyanation/1,2-Brook rearrangement/C- acylation reactions of acylsilanes (4) with cyanoformate esters (7) are described. The products of the reaction are fully substituted malonic acid derivatives (8). Catalysts for this transformation were discovered via a directed candidate screen of 96 metal-ligand complexes. Optimization of a (salen)aluminum complex revealed significant remote electronic effects and concentration effects. The scope of the reaction was investigated by using a number of aryl acylsilanes and cyanoformate esters. Chemoselective reduction of the reaction products (8) afforded new enantioenriched α-hydroxy-α- aryl-β-amino acid derivatives (32-34) and β-lactams (35 and 36). This reaction provides a simple method for the construction of new nitrogen-containing enantioenriched chiral building blocks.
Nicewicz, David A.,Yates, Christopher M.,Johnson, Jeffrey S.
p. 6548 - 6555
(2007/10/03)
Catalytic asymmetric acylation of (silyloxy)nitrile anions
An enantiopure (salen)aluminum alkoxide complex catalyzes the asymmetric coupling of acylsilanes and cyanoformate esters [Eq. (1), R = Bn, Et]. The reactions afford unsymmetrical, fully protected malonic acid derivatives that may be elaborated to nonnatural β-amino acid derivatives, and represent the first asymmetric catalytic reactions involving protected cyanohydrin anions.
Nicewicz, David A.,Yates, Christopher M.,Johnson, Jeffrey S.
p. 2652 - 2655
(2007/10/03)
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