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DOI: 10.1055/sos-SD-027-00847

Schobert, R.; Gordon, G. J.Science of Synthesis, (200427997.

The addition of a base to a phosphonium salt 49 is the most general method for the generation of phosphorus ylides 50 (Scheme 17). Here, a wide range of bases may be employed, varying in strength from butyllithium,[‌13‌,‌282‌,‌306‌,‌307‌] through sodium hydride,[‌308‌] sodium amide,[‌191‌,‌291‌,‌309‌,‌310‌] potassium or sodium hexamethyldisilazanide,[‌282‌,‌311‌,‌312‌] sodium hydroxide,[‌294‌,‌313‌,‌314‌] and sodium alkoxides,[‌142‌,‌315‌,‌316‌] to organic bases such as pyridine[‌187‌,‌294‌] and triethylamine.[‌187‌] The strength of the base used depends on the acidity of the phosphonium salt, which in turn is determined by the substituents adjacent to the ylidic carbon. Weak bases (amines, carbonates, and aqueous alkalis) may be used for the generation of ylides stabilized by electron-withdrawing groups such as esters, ketones, and nitriles. However, phosphonium salts bearing alkyl groups require strong bases (alkyllithiums or alkali metal amides), and a protective gas atmosphere to prevent the unstabilized ylide reacting with the air. Although widely used in organic synthesis, such reactive ylides have rarely been isolated in a highly pure form.

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Meeee Meeeeee/Meeeeeeeee Meeee (%) ee Meeee ee (°M) Mee
88 (M8=M) M/MeMM8, MMM 88.8 88 [‌88‌,‌888‌]
88 (M8=Me) M/MeMM8, MMM 88 888888 [‌888‌,‌888‌]
88 (M8=Me) M/MeMM8, (MMM)8MM, eeeeeee 88 888888 [‌88‌]
88 (M8=Me) M/MeMM8, (MMM)8MM, eeeeeee 88 [‌88‌]
88 (M8=M8M8) MeMe, eeeeeee, eeeeee 88 88.8 [‌888‌]
88 (M8=Me) M8MM8 88 888888 [‌888‌‌888‌]
88 (M8=MM8Me) M/MeMM, M8M 88 888 [‌888‌]
88 [M8=MM(MM8)8MM=MM8] MeMMe, MeMM 88 8888 [‌888‌]
88 (M8=MMMM8MM8Me) MeMM8, M8M 88 888888 [‌888‌,‌888‌]
88 (M8=MM) M/MeMM, MM8Me8, M8M 88 888888 [‌888‌]
Me8M=MMMM MMMMM, MMM, ee 88 8888 [‌888‌]
(MeMM8)8M=MMMe Me8M=MM8 88 888 [‌888‌]

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Meeeeeeeeeee Meeeeeeee

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Meeeee M (eeeeee eeeee eee eeeeeeee eeeeee): M eeeeeeeeee ee MeMM8 (8.88e, 888.8eeee) [eeeeeeeeeeee eeeeeeeee eeeeeeeeeee eeeeee ee, eeeeeeeeee, eeeeeee eeeeeeee eeee Me eee eee MM8 eeee eee eeeeeeee ee eeeeeeeee eeeeeee ee Me(MM8)8] ee eeeee MMM (888eM), eeeeeeeee eeeee ee eeeee eeeeeeeeee ee M8, eee eeeeeee eeee (eeeeee)eeeeeeeeeeeeeeeeeeee eeeeeee (88.8e, 88.8eeee) ee eeeeeee eeeeeeee eeeee eeeeeeee. Mee eeeeeee eee eeeeeee eee eeeeeeee, eeeeeeeee eee eeeee eeeeee eeee eeeeee eee MM8(e) (88.8eeee, 88.8%) eee eeeeeee. Meeee eeeeeee ee ee, eee eeeeeee eee eeeeeeee ee eeeee ee e Meeeeee-eeee eeeeee eeeeee ee eeeeee eeeeeeee MeMM8 eee eee eeeeeeeee MeMe (8.8e ee eeeee). Meeeeeeeeeeee ee eee eeeeeeee eeeee eeeeeee eeeeeeee (88Meee) eeeeeeee e eeeeee eeeeeeeeeee eeeeeeeeeee, eeeee eee eeeee ee 88°M/8.8Meee eee 8e; eeeee: 88.8e (88.8%); ee 88°M; 88MMMM (eeeeeee-e8, δ): 88.8.[‌88‌]

(Meeeeeeeee)eeeeeeeeeeeeeeeeeeee (88, M8=Me); Meeeeee Meeeeeeee:[‌88‌,‌888‌]

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[(Meeeeeeeeeeeeee)eeeeeeeee]eeeeeeeeeeeeeeeeeeee (88, M8=MM8Me); Meeeeee Meeeeeeee:[‌888‌]

Meeeee M (eee eeeeeeeeee eeeeee): (Meeeeeeeeeeeeee)eeeeee(eeeeeeeee)eeeeeeeeeee eeeeeee (888e, 8.88eee) eee eeeeeeeee ee M8M (8M) ee 8888°M. Mee eeee eee eeeeeeee ee eeeeee eeeeeeeee eeeeeeeeee, eee eeeeee ee 8°M. 8M ee MeMM (888eM) eee eeeee eeeeeeee eeeee eeeeeeee eee eeee eeeeeeeeee eeeee e eM ee eeeeeeeeeeeee 8 eee eeeeeee. M eeeeeeeee eeeeeeeeeee eee eeeeeeeee ee e Müeeeee eeeeee, eeeeee eeee eee-eeee M8M, eee eee eeeeeeeee eeeeee eeee eee eeeeeeeeeee ee eee eeeeeee eeeeee ee MM8Me8 (ee. 8888eM). Mee eeeeeee eeeee eee eeeeeeeee, eeeeee eeee M8M, eee eeeee (Me8MM8). Mee eeeeeee eee eeeeeee ee e eeeeee eeeeeeeeee eee eee eeeeeeeee eeeee eee eeeeeeeeeeee (eeeeeee ee MeMMe) ee eeee e eeeeeeeee eeeee eeeeeeeee ee eee eeeeeeee; eeeee: 888e (88%); ee 888°M (MeMMe).

(Meeeeeeeeeeeee)eeeeeeeeeeeeeeeeeeee (88, M8=MM); Meeeeee Meeeeeeee:[‌888‌,‌888‌]

Meeeee M (eee eeeeeeeeee eeeeee): (Meeeeeeeeee)eeeeeeeeeeeeeeeeeeee eeeeeeee (888.8e, 8.88eee) ee M8M (ee. 8888eM) eee eeeeeeee eee eeeeeee eeee MM8Me8 (8888eM). MeMM (88e, 8.88eee) ee M8M (888eM) eee eeeee ee eeee eeeeeeee eeeeee eeeee eeeeeeee eeee e eeeeeee eeeeeeee eee eeeeeeeee eeeeeee eee eM eeeee eeeee 8.8. Mee eeeeeee eeeee eee eeeeeeeee, eeeeee eeee M8M, eee eeeee (MeMM8). Mee eeeeeee eee eeeeeee ee e eeeeee eeeeeeeeee eee eee eeeeeeeee eeeee eee eeeeeeeeeeee (MM8Me8/Me8M 8:8) ee 88°M; eeeee: 888.8e (88 %); ee 888888°M; 88MMMM (MMMe8, δ): 88.8.