The wittig synthesis of allylic organosilicon compounds

A convergent approach for the synthesis of fluorinated sphingosine analogues

“…Direct conversion of aldehyde 8 into allylsilane 7 was first attempted using the Wittig-Seyferth reaction. 9 Using freshly prepared β-trimethylsilylethyltriphenylphosphonium iodide, 10 the reactions consistently led to the formation of complex reaction mixtures which were difficult to purify and the desired allysilane 7 was isolated in a very low yield of 12%. Moreover, the product could never be obtained analytically pure rendering the stereochemical assignment of the double bond ambiguous.…”

Functionalized fluoroalkyl and alkenyl silanes: Preparations, reactions, and synthetic applications

“…The related 4,4,4-trifluoro-2-butenyl(trimethyl)silanes 341 [118] and 343 [124] have been prepared (Scheme 85).…”

The Stereoselective Synthesis of Conjugated Allylsilanes

“…Thus, 2-trimethylsilylethyl-triphenylphosphonium iodide (4) was first prepared and isolated as described by Seyferth et al 4 The treatment of a suspension of 4 in a 5:3 (v/v) solvent mixture of THF/Et 2 O with phenyllithium/Et 2 O 20 affords ylide 5, which reacts in situ with 6c (Scheme 5). After the usual workup, allylsilane 7c was isolated in an E:Z ratio of 98:2 as determined from the 1 H-NMR spectrum.…”

“…Phenyllithium (4 mL of 1.5 molar solution, 6 mmol) in Et 2 O was added dropwise with stirring over 0.5 h to a suspension of 2-trimethylsilyl-ethyltriphenylphosphonium iodide (4), 4 prepared by reacting iodo-methyltrimethylsilane (3) with a freshly prepared solution of methylene-triphenylphosphorane (2) 28 (2.9 g, 6 mmol) in a solvent mixture of abs. THF (10 mL) and abs.…”

“…A relatively straightforward synthetic route to a wide variety of allylsilanes is the Wittig reaction of 2-silyl phosphorus ylides with carbonyl compounds, 4,5,9 which was introduced by Seyferth et al 4 and then modified by Fleming and Paterson. 5 The stereoselectivity of the reaction and subsequently the stereochemistry of the alkenes prepared are highly influenced by the ylide structure, nature of the carbonyl reactant, and experimental conditions.…”