[994-89-8] · C14H28Sn · Tri-n-butylstannylacetylene · (MW 315.13)
(addition of organometallic reagents affords alkenic stannanes; palladium-catalyzed coupling yields enynes; 1,3-dipolarophile)
Physical Data: bp 70 °C/0.2 mmHg; d 1.089 g cm-3.
Solubility: sol common hydrocarbon and ethereal solvents.
Form Supplied in: available from several commercial sources.
Preparative Method: prepared by the reaction of Lithium Acetylide with Tri-n-butylchlorostannane.2
Handling, Storage, and Precautions: organostannane reagents are potentially toxic.3 Therefore their preparation and use must be conducted wearing appropriate protective clothing and in a well ventilated fume hood.
Addition of Tri-n-butylstannane to tributylstannylacetylene (1) affords the synthetically useful reagent trans-1,2-bis(tributylstannyl)ethylene.2 Stannylcupration of (1) with the higher order cuprate (Me3Sn)2Cu(CN)Li2, followed by protonation of the intermediate vinyl cuprate, yields trans-1-(tributylstannyl)-2-(trimethylstannyl)ethylene in excellent yield.4 Hydrozirconation of (1) with Chlorobis(cyclopentadienyl)hydridozirconium and protonation of the intermediate vinylzirconate proceeds smoothly to afford Vinyltributylstannane.5 Addition of Triethylborane to (1) stereospecifically affords (E)-2-(diethylboryl)-1-(tributylstannyl)-1-butene, through an alkynylborate intermediate.6
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 Tributylstannylacetylene (1) couples smoothly with vinyl halides to afford the corresponding enyne in high yield (eq 1).7a The alkene geometry of the starting halide is retained in the product.7 Aryl halides and triflates also couple with (1) to afford the corresponding arylacetylenes.8
Tributylstannylacetylene is an effective 1,3-dipolarophile, reacting with nitrile oxides to afford 5-tributylstannylisoxazoles (eq 2).9 The synthetic utility of this latent 1,3-dicarbonyl equivalent is demonstrated by its straightforward conversion to chromones,9a,b 4(1H)-quinolones, and indoles.9a Tributylstannylpyrazoles are prepared by reaction of (1) with diazoalkanes.10
Tributylstannylacetylene is an effective dienophilic partner in the inverse electron demand Diels-Alder reaction. Stannyl-substituted pyrazines are prepared in moderate yield by reaction with 1,2,4,5-tetrazines.11 Stannyl-substituted pyridines are formed in moderate to poor yields by reaction with (6H)-1,3-oxazin-6-ones (eq 3).12 These compounds are best prepared from the corresponding halo-substituted heterocycles.13
Alfred P. Spada
Rhône-Poulenc Rorer Central Research, Collegeville, PA, USA