42206-19-9Relevant academic research and scientific papers
Overriding felkin control: A general method for highly diastereoselective chelation-controlled additions to α-silyloxy aldehydes
Stanton, Gretchen R.,Johnson, Corinne N.,Walsh, Patrick J.
experimental part, p. 4399 - 4408 (2010/06/14)
According to the Felkin-Anh and Cram-chelation models, nucleophilic additions to α-silyloxy aldehydes proceed through a nonchelation pathway due to the steric and electronic properties of the silyl group, giving rise to Felkin addition products. Herein we describe a general method to promote chelationcontrol in additions to α-silyloxy aldehydes. Dialkylzincs, functionalized dialkylzincs, and (E)-disubstituted, (E)-trisubstituted, and (Z)-disubstituted vinylzinc reagents add to silyl-protected α-hydroxy aldehydes with high selectivity for chelation-controlled products (dr of 10:1 to 20:1) in the presence of alkylzinc halides or triflates, RZnX. With the high functional group tolerance of organozinc reagents, the mild Lewis acidity of RZnX, and the excellent diastereoselectivities favoring the chelation-controlled products, this method will be useful in the synthesis of natural products. A mechanism involving chelation is supported by (1) NMR studies of a model substrate, (2) a dramatic increase in reaction rate in the presence of an alkylzinc halide, and (3) higher diastereoselectivity with larger alkyl substituents on the α-carbon of the aldehyde. This method provides access to chelation-controlled addition products with high diastereoselectivity previously unavailable using achiral organometallic reagents.
Highly enantio- and diastereoselective one-pot methods for the synthesisof halocyclopropyl alcohols
Kim, Hun Young,Salvi, Luca,Carroll, Patrick J.,Walsh, Patrick J.
supporting information; experimental part, p. 954 - 962 (2009/06/28)
The lack of methods for the stereoselective transfer of functionalized carbenoids is one of the most significant deficiencies of Simmons-Smith cyclopropanation reactions. Outlined herein are one-pot methods for the catalytic asymmetric synthesis of halocy
