title: Sequestered alkyllithiums: why phenyllithium alone is suitable for betaine-ylide generation.
abstract: The key step in the trans-selective modification of the Wittig reaction is the alpha-lithiation of the lithium bromide coordinated ylide-aldehyde adduct (the so-called "P-betaine"). Only phenyllithium effects this deprotonation rapidly and cleanly. Alkyllithiums (in particular, butyl-, sec-butyl-, and tert-butyllithium) react only sluggishly and incompletely, being tied up in very stable mixed aggregates with the lithium alkoxide part of the betaines.
authors.affiliation: Institut de Chimie Organique, Université, BCh 1015 Lausanne, Switzerland.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.forename: Dariusz
authors.initials: D
authors.lastname: Deredas
authors.forename: Cyril
authors.initials: C
authors.lastname: Huynh
authors.forename: Manfred
authors.initials: M
authors.lastname: Schlosser