1-Alkenes Methylenetriphenylphosphorane

Methylenetriphenylphosphorane, 254 Titanium(IV) chloride-Lithium aluminum hydride, 310 (Z)-Alkenes By elimination reactions Dichlorobis(cyclopentadienyl)-titanium, 102 Hydrogen peroxide, 145 By hydrogenation of carbon-carbon triple bonds... 

The interaction of the aldehydo derivatives 14a, 14b, and 55 with methylenetriphenylphosphorane has been re-investigated92 with the use of a 1 1 potassium terf-butoxide-fert-butanol complex in the reaction mixture. This modification affords significantly increased yields of the final alkenes (15a, 15b, and their 3-O-benzyl analogs). 

Phosphoranes and phosphonate derived carbanions are also known to react with carbonyl compounds other than aldehydes and ketones, in reactions often referred to as non-classical Wittig reactions.35 Wittig olefination products can be obtained from the reaction of esters, anhydrides and some amides and imides with a range of stabilized and reactive phosphoranes. The reaction of stabilized and semi-stabilized phosphoranes with esters gives alkenes (Scheme 7). However, non-stabilized phosphoranes, such as methylenetriphenylphosphorane, tend to give P-keto phosphoranes on reaction with esters (Scheme 7)—the careful choice of the reaction conditions can also permit the preparation of the alkene in these reactions. 

Four-membered rings. The study of the reaction between thiobenzophenone and methylenetriphenylphosphorane pointed out the presence of a reactive intermediate, thiaphosphetane, which decomposed either to a thiirane and triphenylphosphine or to the Witting alkene and a phosphine sulfide, depending on the temperature. 

Alkene-synthesis using [ C]methylenetriphenylphosphorane (e.g., C-labeled monosaccharides, see Grierson et al. 1993 Ogren et al. 1995b, 1997). 

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