245121-92-0Relevant academic research and scientific papers
Asymmetric nucleophilic acylation of aldehydes via 1,1-heterodisubstituted alkenes
Monenschein, Holger,Draeger, Gerald,Jung, Alexander,Kirschning, Andreas
, p. 2270 - 2280 (2007/10/03)
Aldehydes are asymmetrically acylated by a two step sequence that is initiated by a homologation step to 1,1-heterodisubstituted alkenes followed by asymmetric dihydroxylation. Thus, ketene O,S-acetals are efficiently prepared from aldehydes by a Peterson olefination with lithiated methoxy-phenylthiotrimethylsilyl methane 14 as the C-1 source. Although they are dihydroxylated with the Sharpless catalyst with moderate to good enantioselectivity (62-80% ee), the process is not efficient owing to the low chemical yields of the desired α-hydroxy methyl esters (7-37%). Use of the corresponding sulfoxide 24 or sulfon 25 led to an improved chemical yield of α-hydroxy methyl ester 19, but the stereoselectivity was diminished. In contrast, intermediate ketene O,O-acetals are prepared by a Horner-Wittig reaction with phosphine oxide 31 and are dihydroxylated both with good chemical and stereochemical yield. The concept is applicable to aromatic, aliphatic, and chiral aldehydes. For example, this short sequence allows exclusive and independent preparation of both diastereomeric heptoses 69 a and 69 b.
Rhodium-carbenoid mediated O-H insertion reactions. O-H insertion vs. H-abstraction and effect of catalyst
Cox, Geoffrey G.,Miller, David J.,Moody, Christopher J.,Sie, Eric-Robert H. B.,Kulagowski, Janusz J.
, p. 3195 - 3212 (2007/10/02)
The synthesis and rhodium mediated O-H insertion reactions of a wide range of diazo compounds are described. The rate at which the diazo compounds decompose in the presence of 2-propanol and the rhodium catalyst is strongly dependent on the electron withdrawing group(s) attached to the diazo carbon, with diazophosphonates being the least reactive. Insertion into the O-H bond of methanol, t-butanol and phenols was also investigated, as well as the effect of catalyst. In some cases 'reduction' of the diazo group to the corresponding CH2 group competes with O-H insertion, although this is highly catalyst and substrate dependent. Of the catalysts used, rhodium(II) trifluoroacetamide is the most effective for O-H insertion reactions.
A Convenient one-pot Synthesis of α-Functionalized α,β-Unsaturated Sulfones
Lee, Jae Wook,Oh, Dong Young
, p. 273 - 277 (2007/10/02)
α-Methoxy α,β-unsaturated sulfones and α-chloro α,β-unsaturated sulfones were conveniently prepared in high yields using one-pot Wittig-Horner reaction from methoxymethyl phenyl sulfone and chloromethyl phenyl sulfone, respectively.
