[71504-26-2] · C7H14Si · (E)-1-Trimethylsilyl-1,3-butadiene · (MW 126.30)
(diene for Diels-Alder reactions,2,3 creating allylsilanes that can be converted to a variety of functionalized cyclohexenes with a shift of the double bond from its original position in the cycloaddition;3 synthesis of a chiral allylborane;4 synthesis of allylsilanes5,6 and trienes7)
Physical Data: bp 110-115 °C, 70-74 °C/210 mmHg.
Solubility: freely sol all organic solvents.
Preparative Methods: prepared geometrically pure by Wittig2 or Peterson3 reactions on (E)-3-trimethylsilylpropenal,8 by pyrolysis of silylated 3-sulfolenes,9 and by coupling (E)-2-trimethylsilylvinyl bromide with Lithium Divinylcuprate.10 It can also be prepared geometrically impure, but largely (E), from Allyltrimethylsilane by a vinylogous Ramberg-Bäcklund reaction,11 and from 1,3-Butadienyl-1-magnesium Chloride and Chlorotrimethylsilane.4
Handling, Storage, and Precautions: reasonably stable in the absence of air and radical initiators. It should be kept in a stoppered flask or sealed ampule in the presence of hydroquinone. Its toxicity is unknown, but the presence of a trimethylsilyl group is generally benign.
(E)-1-Trimethylsilyl-1,3-butadiene undergoes Diels-Alder reactions with the usual dienophiles, with unimpaired endo stereoselectivity, but at a somewhat slower rate than 1,3-butadiene itself (eq 1).2,3 The regioselectivity with unsymmetrical dienophiles is poor (eq 2).2,3 The adducts are allylsilanes, which react with electrophiles in the usual way (eqs 3 and 4) to give cyclohexenes with a double bond shifted from the original position.3
Because of the low level of regiocontrol imparted by the silyl group, other substituents on 1-silylated dienes can impart better regiocontrol (eq 5).3
The diene is used as a starting material for the synthesis of the chiral allylborane (1) or its enantiomer (eq 6).4
Reduction of the diene with Lithium and t-butanol in liquid ammonia gives Crotyltrimethylsilane,5 and reaction with Grignard reagents gives longer chain (E)-allylsilanes (eq 7).6
Like other vinylsilanes, 1-trimethylsilyl-1,3-butadiene can be used in a Hiyama coupling reaction with vinyl iodides (eq 8).7
Cambridge University, UK