0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via Variation 1: The SCOOPY Procedure

DOI: 10.1055/sos-SD-047-00004

Schobert, R.; Hölzel, C.; Barnickel, B.Science of Synthesis, (20104761.

The SCOOPY (α-substitution plus carbonyl olefination via β-oxidophosphorus ylides) variant of the Wittig alkenation allows for the concomitant substitution of the ylidic carbon atom with residues other than hydrogen (e.g., alkyl, hydroxymethyl) to give trisubstituted alkenes with defined configuration.[‌14‌,‌15‌,‌466‌‌469‌] In this procedure an unstabilized triphenylphosphonium ylide is prepared from its salt and a lithium base (PhLi or BuLi) and then treated with an aldehyde. The resulting mixtures of the intermediate erythro- and threo-betaines are then deprotonated by adding a second equivalent of the same lithium base at 30°C to give predominantly the lithiated threo-isomer of betaine 129. This can be intercepted by electrophiles other than a proton, giving rise to trisubstituted alkenes 130 with the electrophile located at the original ylidic α-carbon atom and normally positioned cis to the former aldehyde substituent R2 (Scheme 44). SCOOPY reactions have been reported with iodomethane[‌15‌] and, probably most importantly, with formaldehyde to yield trisubstituted E-allylic alcohols.[‌467‌,‌468‌] This hydroxymethylation usually results in a selective loss of the oxyanion from the original carbonyl component regardless of the sequence of addition of the two aldehydes used in this process.[‌469‌] High stereoselectivities are achieved if formaldehyde is added last. When aldehydes other than formaldehyde are used, invariably the oxyanion from the second aldehyde is eliminated as a phosphine oxide.

Meeeee 88 Meeeeeeeeeeeee Meeeeee ee eee MMMMMM Meeeee[‌88‌,‌88‌,‌888‌‌888‌]

Meeeeeeeeee 88

M8 M8 M+ M Meeee (M/M) Meeee (%) ee 888 Mee
Me Me MeM Me 8:88 88 [‌88‌]
Me (MM8)8Me MMMM MM8MM 88:8 88 [‌888‌]
Me Me MMMM MM8MM 88:8 88e [‌888‌]
Me MMMM MM8MM e e [‌888‌]

e Mee eeeeeeeeeeeee 8-eeeeee-8-eeeeeeeeee-8-ee-8-ee (88%) eee eeee eeeeeeee.

e Mee eeeeeee eeeee eee eeeeeeee ee ee M eeeeeeeeeeeeee eee eeeeeeeee eeeeeee eeeeeee eeeeeeeeeeeee.

Meeeeeeeeeee Meeeeeeee

(M)-8-Meeeeee-8-eeeeeeeee-8-eee [888, M8=Me; M8=(MM8)8Me; M=MM8MM]; Meeeeee Meeeeeeee:[‌888‌]

MMMMMMM: Meeeeeeeeeee ee e eeeeeeee eeeee eeeeeeeeee, e eeeeee eee, eeee, eee eeeeeeeeeee eeeee eeeeeeee, eee e eeee eeeeeeeeee.

Meeeeeeeeeeeeeeeeeeeeeeeeeeeee (88.8e, 88eeee), eeeeeee eeeeeeee eeee eeeeeeeeeeeeeeeeeeeeeeeee eeeeeee eee MeMe ee e eeeeeee ee MMM (888eM) eee eeeeee (88eM), eee eeeeee ee 88°M eee eeeeeee ee eeee eeee eeeeeee (88eeee), eeeeeeeee eee eee eeeee ee eee eeeeeee eeeeeeee eeeeeeeeeeeeeee. MeMe (88eeee, 8 eeeee) eee eeeee ee eeee eeeeeeeeeee, eee eee eeeeeee eee eeee eeeeeee ee eeee ee 8°M eee eeeeeee eee 88eee. Meeeeeeee MMMM (88eeee) [eeeeeeee ee eeeeeeeeee e eeeeeee ee eeeeeeeeeeeeeeee (8e), MMM (888eM), eee e eee eeeee ee MM8MMe8 eeee e Meeeeee eeee eeee ee 88°M] eee eeeee ee e 8.8M eeee ee MMM (88eM), eee eee eeeeeeeee eeeeeeeee eeeeeeeeee eee eeeeeee eee 88e ee ee. M8M (88eM) eee eeeee ee eee eeeeeee, eee eeeeeeee eee eeeeeeeee eee eeeeeee 8e. Mee eeeeeeeee eeeeeeeeee eee eeeeeeeeeeee ee eeeeeeeeeee (ee. 888eM ee eeeeeee eee eeeeeee), eeeeeee eeee M8M (888eM), eee eeeeeee eeeeeeeee eeee Me8M (8 × 88eM). Mee eeeeeee eeeeee eeee eeeeeeeee, eeeee, eee eeeeeeeeeeee ee e eeeeee eeeeeeeeee. Mee eeeee eeeeeee eeee eeeeeeee eee eeeeeeee ee eeeeeeeeeeee; eeeee: 8.8e (88%); ee 888888°M/88Meee; (M/M) 88.8:8.8 (ee MM, 88% Meeeeeee eeeeee, 8e, 888°M).