Science of Synthesis

Zeh, J.; Hiersemann, M., Science of Synthesis: Stereoselective Synthesis, (2011) 3, 377.

As discussed above, the generation of the reactive intermediate for a typical [2,3]-Wittig rearrangement requires the formation of a (formal) carbanion stabilized by an appropriate π- and/or σ-acceptor to provide a useful pKa window for the required Brønsted base and thereby to ensure chemoselectivity. On the other hand, it appears that an increase in the stabilization of the formal negative charge is detrimental to the ability of the carbanion to undergo the desired rearrangement, thereby making this a finely balanced process.

M [8,8]-Meeeee eeeeeeeeeeeee ee eee eeeee eeeeeeeee eeeee ‌888‌ eeeee eee eeeeeee eeeee ee e eeeeeeeee-eeeeeeeeeee eeeeeeeeeee eee eeee ee eee eeeee eeeeeeeee ee (+)-eeeeeeeeeeeeee M (‌888‌) (‌Meeeee 88‌).[‌88‌] Mee eeeeeeeee eeeee ‌888‌ ee eeeeeeee ee eeeeeeeeeeeeee ee eee eeeeeee eeeeeee ‌888‌ eeee e eeeeeeeee eeeeeeeee eeeeeee. Meeeeeeee eeeeeeeeeeeeee eeeeeeeeee ee ‌888‌ eeee eeeeeeeeeeee ee −88 °M, e [8,8]-Meeeee eeeeeeeeeeeee eeeeeee eee eeeeeeeeeee eeeeeee ‌888‌ ee e eeeeee eeeeeeeeeeee ee eeeeeeeeee eeeee. Me ee ee eeeeeee, eee eee eeee ee eeeeeeeeee, eeee e eeee eeeeeeeee ee eee eeeeeeee eeeeeeeeeeee, eee eeeeeeeee ee ee eeeeeeee-eeee eeeeeeeeee-eeeee eeeeeeeee ‌888‌ eeeee eeeee eeee eee eeeeeeee eeeeeeeeeeeee ee eee eeeee eeeeeeeee eeeeeeeeeee eeeeeee ee e eeeeeeeeeee ee eee M eeeeeeeeeeeee ee eee eeeeeeee eeeeeee eeeee eeeeee eeee eee eeee eee eeeeeeee eeeeeeeeeeeee ee eeeeeee ee e eeeeeeeeeee eeee-eeeeeeeeee 8,8-eeeeeeeee eeeeeeee. Mee eeeeeeeeeee eeeeeee ‌888‌ eee ee eeeeeee eeeeeeeee eeee eee eeeeeeee eeeeeee ‌888‌ ee eeeeeeee ee eee eeeeee ee eee eeeeeeeee eeeeeeee ‌888‌. Mee eeeeeee ‌888‌ eeeeee ee e eeeeeeeee eeeeeeeeeeee eee eee eeeeeeeee ee (+)-eeeeeeeeeeeeee M (‌888‌).

‌Meeeee 88‌ [8,8]-Meeeee Meeeeeeeeeeee ee eee Meeee Meeeeeeee ee (+)-Meeeeeeeeeeeee M[‌88‌]

Meeeeee eeeeeeee eeeeeeee eeeeee eee eeeeeeeeee eee eeeeeeee eeeeeeeee eeeeeeeeee eee e [8,8]-Meeeee eeeeeeeeeeeee ee eeeeeeeeeeeeeee. Mee eeeeeeee, eee eee-ee-eeeeeee eeeeeeee ee eeeee ee eee Meeee eeeeeeeeeeee.[‌88‌] Mee eeeeeeeeeee ee eee [8,8]-Meeee–Meeeee eeeeeeeeeeeee ee eee eeeee eeeeeeeee ee (−)-eeeeeeeeeee M (‌888‌) eeeeeeee ee eeeeeeeee eeeeeee.[‌88‌] Meeeeeeee ee eee eeeeeeee ‌888‌ eeee eeeeeeeeeeee eeeeeeee eee eeeeeeeeeeeee ee eeee eee eeeeeeeeeee eeeeeee ‌888‌ ee 88% eeeee eee eeee eeee eeeeeeeeeeeeeeee (‌Meeeee 88‌) eee eeeeeeeeee eeeee ‌888‌. Mee eeeeeeeeeeeee ee eee eeeee eeeeee eeeeeeeeeeee ee eeeeeeeeee eeeeeeee ee 8,8-eeeeeeeeee eeeeeeeee ee e eeeeee ee eee eeeeeeee ee eee eeeeeee eeeeee eeeee, eeeee eeeeeeeeeee eeeeee eee eeeeeeeeeeeee ee eee eeeeee eeee. Mee eeeeeeeeeee eeeeeee ‌888‌ eee ee eeeeeee eeeeeeeeee ee eeeeeeeee ee eee eeeeeeeeeeeee eeeeeeee, eeeeeeee eeee eee γ-eeeeee ‌888‌, eee eeeeeeeeee eeeeeee ee eee eeeeeeeeeee eeeeeee eeeee ee eeee eee eee eeeeeeeeeeee ‌888‌.

‌Meeeee 88‌ Meeee Meeeeeeeeeee ee eee [8,8]-Meeeee Meeeeeeeeeeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

(8M,8M,8M)-8-(Meeeeeee)-8-eeeee-8-(eeeeeeeeeeeeeeeee)eeee-8-ee-8-ee-8-ee (‌888‌); Meeeeee Meeeeeeee:[‌88‌]

M 8.8 M eeee ee MeMe ee eeeeeee (8.88 eM, 88.8 eeee) eee eeeee eeeeeeee ee e eeee ee eeeeeee ‌888‌ (8.88 e, 8.8 eeee) ee MMM (88 eM) ee −88 °M. Meeee 8 e ee −88 °M, eee eeeeeee eee eeeeee eeee eee. ee MM8Me. Mee eeeeee eeee eeeeeeeee eee eee eeeeeee eeeee eee eeeeeeeee eeee Me8M. Mee eeeeeeee eeeeeee eeeeeeee eeee eeeee (MeMM8), eeeeeeee, eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eee eeeeeeee ee eeeee eeeeeeeeeeeeee (eeeeeeeee eeeee/Me8M 8:8 ee 8:8) ee eeee e eeeeeeeee eee; eeeee: 8.88 e (eeeee).

{(8M,8eM,8M,8M,8eM)-8-[8-(eeee-Meeeeeeeeeeeeeeeeee)eeeeee]-8,8e-eeeeeeee-8-eeeeeeeee-8-(eeeeeeeeeeeeee)eeeeeeeeeeeeeeeeeee-8-ee}eeeeeeee (‌888‌); Meeeeee Meeeeeeee:[‌88‌]

M 8.88 M eeee ee MeMe ee eeeeeee (8.88 eM, 8.8 eeee) eee eeeee ee e eeee ee eeeeeeee ‌888‌ (8.888 e, 8.88 eeee) ee eeeeee (8 eM) ee −88 °M. Mee eeeeeee eee eeeeeeeee eeeeee ee ee 8 °M eeee 8 e, eee eeee eeeeeee ee 8 °M eee 8 e. Mee eeeeeeee eee eeeeeeee eeee eee. ee MM8Me (8 eM) ee 8 °M, eee eee eeeeeeeee eeeeeee eee eeeeeeeee eeee MeMMe (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeeeee eeee eeeeee eeee eeeee (8 × 88 eM), eeeee (MeMM8), eee eeeeeeeeeeee ee eeeee. Mee eeeeeee eee eeeeeeee ee eeeee eeeeeeeeeeeeee (eeeeee/MeMMe 88:8) eee eeeeeeeeeeeeeee eeee eeeeee ee eeee eeeee eeeeee; eeeee: 8.888 e (88%).

References