Science of Synthesis

Schobert, R.; Hölzel, C.; Barnickel, B., Science of Synthesis, (2010) 47, 49.

In 1966 Schlosser and Christmann reported the first example of a highly E-selective Wittig alkenation using unstabilized ylides.[‌345‌] This protocol later came to be known as the Wittig–Schlosser reaction or the Schlosser modification of the Wittig alkenation.[‌11‌,‌374‌,‌375‌] An unstabilized ylide ‌102‌, prepared from the corresponding phosphonium salt and an organolithium base (PhLi or BuLi) containing additional lithium bromide, is treated with an aldehyde at −78°C. The resulting mixture of erythro- and threo-betaines ‌103‌ is deprotonated by a second equivalent of the same lithium base at −30°C to give the lithiated betaines ‌104A‌ and ‌104B‌ with the latter prevailing in the equilibrium. Reprotonation by addition of anhydrous hydrochloric acid in diethyl ether or tert-butyl alcohol converts the lithiated betaine ‌104B‌ into threo-‌103‌, which collapses upon treatment with potassium tert-butoxide or heating to the corresponding E-alkene ‌105‌ with selectivities typically greater than 98:1 (‌Scheme 36‌).

‌Meeeee 88‌ Meeeee–Meeeeeeee M-Meeeeeeeee eee β-Meeeeeeeeeeeeeee Meeeee[‌888‌,‌888‌–‌888‌]

‌Meeeeeeeeee 88‌

M8	M8	Meeeeeee	Meeee (M/M)	Meeee (%) ee ‌888‌	Mee
(MM8)8Me	Me	MeMe, MMe	<8.8:88.8e	88	[‌888‌]
eMe	(MM8)8Me	MeMe, MMe	<8.8:88.8e	88	[‌888‌]
Me	Me	MeMe, MMe	<8.8:88.8e	88	[‌888‌]
Me	(MM8)8MM	MeMe, MMe	8:88e	88	[‌888‌]
(MM8)8Me		MeMe, MeMM	88:88	88e	[‌888‌]
		MeMe, MeMM	88:88	88	[‌888‌]
(MM8)8MM8Me	(MM8)8Me	MeMee	M eeee	88	[‌888‌]
(MM8)8Me		e-MeMe, MeMM	88:88	88	[‌888‌]
		MeMe, MMe	–e	88	[‌888‌]

e Meeeeeeeee ee MM.

e Meeee eeeeee ee eee eeeeeeeeeeeee eeeeeee eeeee MMMM eeeeeeeeeeee.

e Meeeeee eeeeeee eee MMe eee eeeee; eee eeeeee eee eeeeee ee eeeeeeee ee ee eee 8 e.

e Me eeee eeeee; eeeeeee eeeee eeeeee M-eeeeee.

Meeeeeeeeeee Meeeeeeee

Meeeeee ‌888‌; Meeeeee Meeeeeeee:[‌888‌]

Mee eeeeeeeeeee eeee (88 eeee) eee eeeeeeeee ee eeeee MMM (88 eM) eee eeeee Me8M (88 eM) eee eee eeee eee eeeeeee eeee MeMe (88 eeee) ee Me8M eeeee eee Meeeee eeee eee eeeeeeee (eeeee 88 eee). Mee eeee eee eeeeee ee −88°M, eee eee eeeeeeeeeee eeeeeeee (88 eeee) eeeeeeeee ee Me8M (88 eM) eee eeeee. Mee eeeeeee eee eeeeeee eeeeeeeeee eeeee eeeeeeee eeeeeeeeeeeeee eee eeeeeeee (8 eee ee −88 ee −88°M), eeee eeeeeee MeMe (88 eeee) ee Me8M eee eeeee, eee eee eeeeeee eee eeee ee −88°M eeeee e eeeeeeee Meeeee eeee eeeeeeeee eeeeeeee eeeeeeeeeee ee MeMe. Meeeeeeeeeee, eee eeee eee eeeeeee eeee eeeeeeee MMe (88 eeee) eee eeee e-MeMM ee eeeeeeeeeee eeee e-MeMM (8:8; 88 eeee). Mee eeeeeee eee eeeeeee ee eeee ee ee, eeeeeee eee eeeeeee 8 e, eee eeeeeee eeeeeeeeeee ee eeeeee e eeeee eeeeeeeeeee eeeeee. Mee eeeeeee eeeee eee eeeeee eeee M8M, eeeee, eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeee eeeeee eee eeeeeee eeeeeeee ee eeeeeeeeeeee ee eeeeee eeeeeeeeeeeeee.

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) M 8e, 888.