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20.5.14.1.4.1 Variation 1: Wittig Reaction

DOI: 10.1055/sos-SD-020-01227

Vanderwal, C. D.; Jacobsen, E. N.Science of Synthesis, (2007201321.

The reaction of aldehydes, and to a lesser extent ketones, with ester-stabilized phosphonium ylides is a well established protocol for the formation of alk-2-enoic acid esters.[‌51‌,‌52‌] The reaction is tolerant of most functional groups used in complex synthesis, and often affords products with high E/Z selectivity. Some of the myriad uses of this reaction are exemplified in Scheme 17. Bicyclopropylidene-2-carbaldehyde (85) is converted in nearly quantitative yield into alk-2-enoic acid ester 86;[‌53‌] similarly, aldehyde 87 is homologated to 88 with high efficiency.[‌54‌] α-Substituted phosphoranes also react smoothly with aldehydes to generate trisubstituted alkenes; the condensation of phosphorane 89 with aldehyde 90 to afford alk-2-enoic acid ester 91 is representative.[‌55‌,‌56‌] Although more challenging, relatively unhindered ketones are also suitable substrates, as shown in the conversion of pyrrolidinone 92 into diester 93.[‌57‌]

Meeeee 88 Meeeee Meeeeeee eee eee Meeeeeeee ee Mee-8-eeeee Meee Meeeee[‌88‌‌88‌]

Meeeeeeeeeee Meeeeeeee

Meeeee (M)-8-(Meeeeeeeeeeeeeeee-8-ee)eeeeeeee (88); Meeeeee Meeeeeeee:[‌88‌]

M eeee ee eeeeeeee 88 (8.88e, 88.8eeee) eee eeeeee (eeeeeeeeeeeeeeeeeeeeeeeeee)eeeeeee (88.8e, 88.8eeee) ee eeeee MM8Me8 (888eM) eee eeeeeee ee eeeeeee eeeeeeeeeee eee 88e. Meeeeee (888eM) eee eeeee, eee eee eeeeeeeee eeeeeee eee eeeeeee eee 8e eee eeeeeeee (eeeeee eee, 888e ee e 8-ee eeeee eee). Mee eeeeee eee eee eeeeee (eeeeeee/MM8Me8 8:8, 888eM), eee eee eeeeeeee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee ee eeeeee eee-8-eeeee eeee eeeee 88 ee eeee eeeeee; eeeee: 8.88e (88%).

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