[14275-61-7] · C26H56Sn2 · trans-1,2-Bis(tributylstannyl)ethylene · (MW 606.11)
(versatile vinyl anion synthon: efficiently monotransmetalated by alkyllithium reagents2 and higher order organocuprates;7,8 palladium-catalyzed coupling with a variety of electrophilic partners affords substituted vinylstannanes)
Solubility: sol THF, DMF.
Analysis of Reagent Purity: TLC.4
Handling, Storage, and Precautions: organostannane reagents are potentially toxic.6 Their preparation and use must therefore be conducted, wearing appropriate protective clothing, in a well ventilated fume hood. The reagent should be stored under an inert atmosphere and protected from light.
Alkyllithium reagents efficiently transmetalate (E)-1,2-(bistributylstannyl)ethylene (1) to afford (E)-1-lithio-2-(tributylstannyl)ethylene, which exhibits reactivity typical of vinyllithium reagents.2,3
Higher order cyanocuprates (Me2CuCNLi2 and Me(2-Th)CuCNLi2) rapidly transmetalate (E)-1,2-(bistributylstannyl)ethylene in high yield at ambient temperature to afford the corresponding vinylcuprates (n-Bu3SnCH=CH)(Me)Cu(CN)Li27 and (n-Bu3SnCH=CH)(2-Th)Cu(CN)Li2,8 thus providing a very convient method for the preparation these useful reagents.7-9
Stille et al. pioneered the palladium-catalyzed cross-coupling reaction of organostannanes with a variety of electrophilic partners. These reactions proceed under mild conditions which are often compatable with typically sensitive functional groups.1
Palladium-catalyzed coupling of (E)-1,2-(bistributylstannyl)ethylene with appropriate electrophiles can afford either mono- or disubstituted products. The product distribution is readily and predictably controlled by the stoichiometry of the reactants. Coupling of (1) with 1 equiv of an allylic (eq 1),10a aromatic,11 or vinyl halide12 provides the corresponding substituted vinylstannane. Symmetrical stilbenes are prepared when 2 equiv of aryl halide are used.13
Macrocylization of the highly functionalized divinyl diiodide (2) (eq 2)14 to rapamycin (3) is an elegant and unique example of the use of this reagent.
b-Stannyl enones are prepared in moderate yield by the palladium-catalyzed coupling of (E)-1,2-(bistributylstannyl)ethylene with acyl chlorides (eq 3).15 Coupling of the product with a second acyl chloride provides a route to unsymmetrical 1,4-butanediones. The intermediate 1,4-butenediones are efficiently reduced in situ by a palladium hydride species generated during the course of the reaction.15 Symmetrical 1,4-butanediones are prepared directly when 2 equiv of acid chloride are used.15
Aluminum Chloride-promoted coupling of (E)-1,2-bis(tributylstannyl)ethylene with acid chlorides provides an alternate, and often higher yielding, route to b-stannyl enones.3b,16
Alfred P. Spada
Rhône-Poulenc Rorer Central Research, Collegeville, PA, USA