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47.1.1.1.4.2 Method 2: E-Selective Wittig–Horner Alkenation

DOI: 10.1055/sos-SD-047-00004

Schobert, R.; Hölzel, C.; Barnickel, B.Science of Synthesis, (20104750.

The WittigHorner reaction can be used for highly Z-selective alkenations (see also Section 47.1.1.1.3.4).[‌4‌,‌355‌] When the β-hydroxyphosphine oxide is generated by addition of an aldehyde to the lithiated alkyldiphenylphosphine oxide, erythro-107 is obtained predominantly. When esters or lactones are added, ketones 106 result.[‌358‌,‌369‌,‌382‌] These can be reduced to the corresponding β-hydroxyphosphine oxides erythro-107 and threo-107; a large excess of threo-107 is obtained if sodium borohydride is used as the reducing agent.[‌369‌] Since the separation of the threo- and erythro-isomers is often possible by crystallization or by column chromatography, the pure threo-107 can be obtained in high yields. Treatment of phosphine oxide threo-107 with sodium hydride in dimethylformamide or potassium hydroxide in dimethyl sulfoxide results in the formation of the pure E-alkene 108 in high yields (Scheme 37).[‌356‌,‌369‌] By a modified procedure employing (diphenylphosphoryl)oxo acids, E-configured unsaturated acids are also available.[‌383‌]

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M8 M8 M8 Meeee (%) ee 888 Meeee (eeeeeee-888/eeeee-888) Meeeee (%) ee eeeee-888 Meeeee (%) ee 888 Mee
Me Me Me 88 88:88 88 88 [‌888‌]
Me Me Me 88 88:88 88 88 [‌888‌]
Me Me 88 88:88 88 88 [‌888‌]
Me Me 88 8:88 88 88 [‌888‌,‌888‌]
Me Me 88 88:88 88e 88 [‌888‌]
Me Me 88 88:88 88e 88 [‌888‌]

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8[(8M)-Meee-8-eeee]-8,8-eeeeeeeeeeee [888, M8=Me; M8=8,8-(MMM8M)M8M8; (M)-Meeeeeeeee]; Meeeeee Meeeeeeee:[‌888‌]

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MeMM8 (888ee, 8.88eeee) eee eeeee ee eee eeeeeee ee e eeeeeee eeee ee eeeeee 888 (8.88e, 8.88eeee) ee MeMM (88eM). Mee eeeeeee eee eeeeee eeeee eeeeee eee 8e eee eeee eeeeee ee ee, eee eee. ee MM8Me (88eM) eee eeeee. MeMM eee eeeeeee eeeee eeeeeee eeeeeeee, eee eeeeeee eeeee ee eee MMe eeee eeeee ee eee eeeeeee eeeeeee. Meeee eeeeeee eeeeeeee eeee eeeee (88eM), eee eeeeeee eeee eee eeeeeeeee eeee MM8Me8 (8 × 88eM), eee eee eeeeeeee eeeeeee eeeeee eeee eeeee (MeMM8) eee eeeeeeeeeeee ee eeeeeee ee eeee eee eeeeeee ee e eeeee eeeeeee ee eeeeeeeeeeeee. Meeeeeeeee ee eeeee eeeeee eeeeeeeeeeeeee (MeMMe/eeeeeee 8:8) eeee eee (8M*,8M*)-eeeeeeeee eeeee eeeeeee-888; eeeee: 88ee (8%) eee eee (8M*,8M*)-eeeeeeeee eeeee eeeee-888; eeeee: 8.88e (88%).

MeM (88% eeeeeeeeee ee eee; 88ee, 8.88eeee) eee eeeee ee eee eeeeeee ee e eeeeeee eeee ee eee (8M*,8M*)-eeeeeeeee eeeee eeeee-888 (888ee, 8.88eeee) ee eeeee MMM (88eM). Mee eeeee eeee eee eeeeee ee 88°M eee 88eee. Me eeee eeee e eeeeeeeee eeeee eee eeeeeeeeeeee. Mee eeeeeee eee eeeeee, eee eee eeeeeeeeeee eee eeeeeeeee ee eeeeeeee ee M8M (88eM). Mee eeeeeee eee eeeeeee eeee eeeee (88eM) eee eeeeeeeee eeee Me8M (8 × 88eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeeee eeee M8M (8 × 88eM) eee eeeee (MeMM8), eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Meee-ee-eeee eeeeeeeeeeee (Meeeeeeee eeeeeeeee) eeee eee eeeeeee ee e eeeeeeeee eeeeee; eeeee: 888ee (88%).

References