90270-52-3Relevant articles and documents
First successful metal coordination control in 1,3-dipolar cycloadditions. High-rate acceleration and regio- and stereocontrol of nitrile oxide cycloadditions to the magnesium alkoxides of allylic and homoallylic alcohols
Kanemasa, Shuji,Nishiuchi, Masaki,Kamimura, Akio,Hori, Kenzi
, p. 2324 - 2339 (2007/10/02)
The first successful control of stereo- and regioselectivity in 1,3-dipolar cycloadditions by metal coordination is described. The presence of magnesium ions dramatically accelerates nitrile oxide dipolar cycloadditions to allylic alcohols, improving both the regio- and stereoselectivity of the reaction. For example, cycloadditions to terminal allylic alcohols bearing α-chirality produce syn-stereoisomers of 2-isoxazolines selectively, and reactions involving the magnesium alkoxides of internal allylic alcohols are exclusively regioselective in favor of 5-hydroxymethyl-2-isoxazolines. Metal alkoxides other than magnesium, such as lithium, zinc, and aluminum alkoxides, are less effective. These reactions involve the formation of activated intermediates in which a nitrile oxide and an allylic alkoxide coordinate to the magnesium ion. Theoretical calculations indicate that the formation of the coordinated intermediates enhances the rate of cycloaddition and also improves the syn-selectivity.
Generation of nitrile oxides through O-metalation of hydroximoyl chlorides. Chelation-controlled syn-selective cycloaddition of nitrile oxides to α-substituted allyl alcohols
Kanemasa, Shuji,Kobayashi, Shigeru,Nishiuchi, Masaki,Yamamoto, Hidetoshi,Wada, Eiji
, p. 6367 - 6370 (2007/10/02)
New generation of nitrile oxides by treatment of hydroximoyl chlorides with organometallics is reported. Their cycloadditions to the allyl alcohols bearing a chiral center at the 1-position proceed in a syn-selective manner, providing the first example of
