[55723-10-9] · C20H40O2Sn · (E)-3-Tri-n-butylstannyl-2-propenyl 2-Tetrahydropyranyl Ether · (MW 431.31)
(efficiently transmetalated by alkyllithium reagents;2 palladium-catalyzed coupling affords substituted allylic alcohols)
Solubility: sol THF, DMF.
Handling, Storage, and Precautions: organostannane reagents are potentially toxic. Therefore their preparation and use must be conducted wearing appropriate protective clothing and in a well-ventilated hood. The reagent should be stored under an inert atmosphere and protected from light.
Alkyllithium reagents efficiently transmetalate (E)-3-tributylstannyl-2-propenyl 2-tetrahydropyranyl ether (1) to afford (E)-3-lithiopropenyl 2-tetrahydropyranyl ether, which exhibits reactivity typical of vinyllithium reagents.2
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 compatible with typically sensitive functional groups.1 Palladium-catalyzed couplings of (1) with vinyl halides (eq 1)5 and heteroaryl halides (eq 2)6 have been reported. Coupling of (1) (7:1 E/Z ratio) with aromatic triflates affords a 3:1 mixture of alkenic products (eq 3).7a Isomerically pure allylic alcohols can be obtained directly from the palladium-catalyzed coupling of (E)- and (Z)-1-(tributylstannyl)-1-propen-3-ol with aromatic triflates.7a
Aromatic triflates7b and allylic halides8 couple with (1) in the presence of carbon monoxide to afford the corresponding a,b-unsaturated ketones (eq 4).7b
Coupling of (1) (1:1 E/Z ratio) with sulfonyl chlorides affords the corresponding isomerically pure (E)-allylic sulfone in good yield (eq 5).9 Presumably, a mixture of allylic sulfones is formed initially which subsequently isomerizes under the reaction conditions to provide the thermodynamically more stable (E)-isomer. Similar isomerizations are observed in the palladium-catalyzed coupling of acid chlorides with (Z)-vinylstannanes.10
Alfred P. Spada
Rhône-Poulenc Rorer Central Research, Collegeville, PA, USA