0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login or sign up for a free trial to access the full content. Variation 4: The Peterson Alkenation

DOI: 10.1055/sos-SD-020-01227

Vanderwal, C. D.; Jacobsen, E. N.Science of Synthesis, (2007201324.

The Peterson reaction, which makes use of silicon-stabilized carbanions to effect alkenation of carbonyl compounds, is not used as often for the introduction of alk-2-enoic acid esters as are the Wittig and the HornerWadsworthEmmons reactions. This is presumably due in most part to the relative difficulty associated with the preparation of complex C-silylated esters, as well as the lack of geometrical selectivity that can plague this method. Nonetheless, the Peterson reaction does have some advantages, such as the increased reactivity of the silyl-stabilized carbanions compared to the corresponding Wittig and HornerWadsworthEmmons reagents, and the lack of phosphine oxide byproducts that accompany the use of phosphorane chemistry. Thus, the Peterson alkenation has seen some use in the context of alk-2-enoic acid ester synthesis,[‌69‌] and two examples are shown in Scheme 20. Conversion of hindered aldehyde 111 into ester 112 proceeds in very high yield and with excellent geometrical selectivity;[‌70‌] excellent results are also obtained in the alkenation of ketone 113 to deliver alk-2-enoic acid ester 114.[‌71‌] Only the direct formation of alk-2-enoic acid esters from carbonyl compounds, and not the two-step variant that includes isolation of the β-silyl alcohol intermediate, is detailed here; for a discussion of β-silyl alcohols and their elimination chemistry, please refer to Science of Synthesis, Vol. 4 [Compounds of Group 15 (As, Sb, Bi) and Silicon Compounds (Section 4.4.374.4.37)]. The use of germanium-stabilized carbanions in geometrically selective Peterson-type alkenations has also been reported.[‌72‌]

Meeeee 88 Mee-8-eeeee Meee Meeeee eeee eee Meeeeeee Meeeeeee[‌88‌,‌88‌]